SQL is divided into the following
Data Definition Language (DDL)
Data Manipulation Language (DML)
Data Retrieval Language (DRL)
Transaction Control Language (TCL)
Data Control Language (DCL)
DDL -- create, alter, drop, truncate, rename
DML -- insert, update, delete
DRL -- select
TCL -- commit, rollback, savepoint
DCL -- grant, revoke
CREATE TABLE SYNTAX
Create table
Ex:
SQL> create table student (no number (2), name varchar (10), marks number (3));
INSERT
This will be used to insert the records into table.
We have two methods to insert.
By value method
By address method
a) USING VALUE METHOD
Syntax:
insert into
Ex:
SQL> insert into student values (1, ’sudha’, 100);
SQL> insert into student values (2, ’saketh’, 200);
To insert a new record again you have to type entire insert command, if there are lot of
records this will be difficult.
This will be avoided by using address method.
b) USING ADDRESS METHOD
Syntax:
insert into
Ex:
SQL> insert into student values (&no, '&name', &marks);
Enter value for no: 1
Enter value for name: Jagan
Enter value for marks: 300
old 1: insert into student values(&no, '&name', &marks)
new 1: insert into student values(1, 'Jagan', 300)
SQL> /
Enter value for no: 2
Enter value for name: Naren
Enter value for marks: 400
old 1: insert into student values(&no, '&name', &marks)
new 1: insert into student values(2, 'Naren', 400)
c) INSERTING DATA INTO SPECIFIED COLUMNS USING VALUE METHOD
Syntax:
insert into
Ex:
SQL> insert into student (no, name) values (3, ’Ramesh’);
SQL> insert into student (no, name) values (4, ’Madhu’);
d) INSERTING DATA INTO SPECIFIED COLUMNS USING ADDRESS METHOD
Syntax:
insert into
Ex:
SQL> insert into student (no, name) values (&no, '&name');
Enter value for no: 5
Enter value for name: Visu
old 1: insert into student (no, name) values(&no, '&name')
new 1: insert into student (no, name) values(5, 'Visu')
SQL> /
Enter value for no: 6
Enter value for name: Rattu
old 1: insert into student (no, name) values(&no, '&name')
new 1: insert into student (no, name) values(6, 'Rattu')
SELECTING DATA
Syntax:
Select * from
or
Select col1, col2, … coln from
Ex:
SQL> select * from student;
NO NAME MARKS
--- ------ --------
1 Sudha 100
2 Saketh 200
1 Jagan 300
2 Naren 400
3 Ramesh
4 Madhu
5 Visu
6 Rattu
SQL> select no, name, marks from student;
NO NAME MARKS
--- ------ --------
1 Sudha 100
2 Saketh 200
1 Jagan 300
2 Naren 400
3 Ramesh
4 Madhu
5 Visu
6 Rattu
SQL> select no, name from student;
NO NAME
--- -------
1 Sudha
2 Saketh
1 Jagan
2 Naren
3 Ramesh
4 Madhu
5 Visu
6 Rattu
CONDITIONAL SELECTIONS AND OPERATORS
We have two clauses used in this
Where
Order by
USING WHERE
Syntax:
select * from
the following are the different types of operators used in where clause.
Arithmetic operators
Comparison operators
Logical operators
Arithmetic operators -- highest precedence
+, -, *, /
Comparison operators
=, !=, >, <, >=, <=, <>
between, not between
in, not in
null, not null
like
Logical operators
And
Or -- lowest precedence
not
a) USING =, >, <, >=, <=, !=, <>
Ex:
SQL> select * from student where no = 2;
NO NAME MARKS
--- ------- ---------
2 Saketh 200
2 Naren 400
SQL> select * from student where no < 2;
NO NAME MARKS
--- ------- ----------
1 Sudha 100
1 Jagan 300
SQL> select * from student where no > 2;
NO NAME MARKS
--- ------- ----------
3 Ramesh
4 Madhu
5 Visu
6 Rattu
SQL> select * from student where no <= 2;
NO NAME MARKS
--- ------- ----------
1 Sudha 100
2 Saketh 200
1 Jagan 300
2 Naren 400
SQL> select * from student where no >= 2;
NO NAME MARKS
--- ------- ---------
2 Saketh 200
2 Naren 400
3 Ramesh
4 Madhu
5 Visu
6 Rattu
SQL> select * from student where no != 2;
NO NAME MARKS
--- ------- ----------
1 Sudha 100
1 Jagan 300
3 Ramesh
4 Madhu
5 Visu
6 Rattu
SQL> select * from student where no <> 2;
NO NAME MARKS
--- ------- ----------
1 Sudha 100
1 Jagan 300
3 Ramesh
4 Madhu
5 Visu
6 Rattu
b) USING AND
This will gives the output when all the conditions become true.
Syntax:
select * from
Ex:
SQL> select * from student where no = 2 and marks >= 200;
NO NAME MARKS
--- ------- --------
2 Saketh 200
2 Naren 400
c) USING OR
This will gives the output when either of the conditions become true.
Syntax:
select * from
Ex:
SQL> select * from student where no = 2 or marks >= 200;
NO NAME MARKS
--- ------- ---------
2 Saketh 200
1 Jagan 300
2 Naren 400
d) USING BETWEEN
This will gives the output based on the column and its lower bound, upperbound.
Syntax:
select * from
Ex:
SQL> select * from student where marks between 200 and 400;
NO NAME MARKS
--- ------- ---------
2 Saketh 200
1 Jagan 300
2 Naren 400
e) USING NOT BETWEEN
This will gives the output based on the column which values are not in its lower bound,
upperbound.
Syntax:
select * from
Ex:
SQL> select * from student where marks not between 200 and 400;
NO NAME MARKS
--- ------- ---------
1 Sudha 100
f) USING IN
This will gives the output based on the column and its list of values specified.
Syntax:
select * from
Ex:
SQL> select * from student where no in (1, 2, 3);
NO NAME MARKS
--- ------- ---------
1 Sudha 100
2 Saketh 200
1 Jagan 300
2 Naren 400
3 Ramesh
g) USING NOT IN
This will gives the output based on the column which values are not in the list of values
specified.
Syntax:
select * from
Ex:
SQL> select * from student where no not in (1, 2, 3);
NO NAME MARKS
--- ------- ---------
4 Madhu
5 Visu
6 Rattu
h) USING NULL
This will gives the output based on the null values in the specified column.
Syntax:
select * from
Ex:
SQL> select * from student where marks is null;
NO NAME MARKS
--- ------- ---------
3 Ramesh
4 Madhu
5 Visu
6 Rattu
i) USING NOT NULL
This will gives the output based on the not null values in the specified column.
Syntax:
select * from
Ex:
SQL> select * from student where marks is not null;
NO NAME MARKS
--- ------- ---------
1 Sudha 100
2 Saketh 200
1 Jagan 300
2 Naren 400
j) USING LIKE
This will be used to search through the rows of database column based on the pattern you
specify.
Syntax:
select * from
Ex:
i) This will give the rows whose marks are 100.
SQL> select * from student where marks like 100;
NO NAME MARKS
--- ------- ---------
1 Sudha 100
ii) This will give the rows whose name start with ‘S’.
SQL> select * from student where name like 'S%';
NO NAME MARKS
--- ------- ---------
1 Sudha 100
2 Saketh 200
iii) This will give the rows whose name ends with ‘h’.
SQL> select * from student where name like '%h';
NO NAME MARKS
--- ------- ---------
2 Saketh 200
3 Ramesh
iV) This will give the rows whose name’s second letter start with ‘a’.
SQL> select * from student where name like '_a%';
NO NAME MARKS
--- ------- --------
2 Saketh 200
1 Jagan 300
2 Naren 400
3 Ramesh
4 Madhu
6 Rattu
V) This will give the rows whose name’s third letter start with ‘d’.
SQL> select * from student where name like '__d%';
NO NAME MARKS
--- ------- ---------
1 Sudha 100
4 Madhu
Vi) This will give the rows whose name’s second letter start with ‘t’ from ending.
SQL> select * from student where name like '%_t%';
NO NAME MARKS
--- ------- ---------
2 Saketh 200
6 Rattu
Vii) This will give the rows whose name’s third letter start with ‘e’ from ending.
SQL> select * from student where name like '%e__%';
NO NAME MARKS
--- ------- ---------
2 Saketh 200
3 Ramesh
Viii) This will give the rows whose name cotains 2 a’s.
SQL> select * from student where name like '%a% a %';
NO NAME MARKS
--- ------- ----------
1 Jagan 300
* You have to specify the patterns in like using underscore ( _ ).
USING ORDER BY
This will be used to ordering the columns data (ascending or descending).
Syntax:
Select * from
By default oracle will use ascending order.
If you want output in descending order you have to use desc keyword after the column.
Ex:
SQL> select * from student order by no;
NO NAME MARKS
--- ------- ---------
1 Sudha 100
1 Jagan 300
2 Saketh 200
2 Naren 400
3 Ramesh
4 Madhu
5 Visu
6 Rattu
SQL> select * from student order by no desc;
NO NAME MARKS
--- ------- ---------
6 Rattu
5 Visu
4 Madhu
3 Ramesh
2 Saketh 200
2 Naren 400
1 Sudha 100
1 Jagan 300
USING DML
USING UPDATE
This can be used to modify the table data.
Syntax:
Update
Ex:
SQL> update student set marks = 500;
If you are not specifying any condition this will update entire table.
SQL> update student set marks = 500 where no = 2;
SQL> update student set marks = 500, name = 'Venu' where no = 1;
USING DELETE
This can be used to delete the table data temporarily.
Syntax:
Delete
Ex:
SQL> delete student;
If you are not specifying any condition this will delete entire table.
SQL> delete student where no = 2;
USING DDL
USING ALTER
This can be used to add or remove columns and to modify the precision of the datatype.
a) ADDING COLUMN
Syntax:
alter table
Ex:
SQL> alter table student add sdob date;
b) REMOVING COLUMN
Syntax:
alter table
Ex:
SQL> alter table student drop column sdob;
c) INCREASING OR DECREASING PRECISION OF A COLUMN
Syntax:
alter table
Ex:
SQL> alter table student modify marks number(5);
* To decrease precision the column should be empty.
d) MAKING COLUMN UNUSED
Syntax:
alter table
Ex:
SQL> alter table student set unused column marks;
Even though the column is unused still it will occupy memory.
d) DROPPING UNUSED COLUMNS
Syntax:
alter table
Ex:
SQL> alter table student drop unused columns;
* You can not drop individual unused columns of a table.
e) RENAMING COLUMN
Syntax:
alter table
Ex:
SQL> alter table student rename column marks to smarks;
USING TRUNCATE
This can be used to delete the entire table data permanently.
Syntax:
truncate table
Ex:
SQL> truncate table student;
USING DROP
This will be used to drop the database object;
Syntax:
Drop table
Ex:
SQL> drop table student;
USING RENAME
This will be used to rename the database object;
Syntax:
rename
Ex:
SQL> rename student to stud;
USING TCL
USING COMMIT
This will be used to save the work.
Commit is of two types.
Implicit
Explicit
a) IMPLICIT
This will be issued by oracle internally in two situations.
When any DDL operation is performed.
When you are exiting from SQL * PLUS.
b) EXPLICIT
This will be issued by the user.
Syntax:
Commit or commit work;
* When ever you committed then the transaction was completed.
USING ROLLBACK
This will undo the operation.
This will be applied in two methods.
Upto previous commit
Upto previous rollback
Syntax:
Roll or roll work;
Or
Rollback or rollback work;
* While process is going on, if suddenly power goes then oracle will rollback the transaction.
USING SAVEPOINT
You can use savepoints to rollback portions of your current set of transactions.
Syntax:
Savepoint
Ex:
SQL> savepoint s1;
SQL> insert into student values(1, ‘a’, 100);
SQL> savepoint s2;
SQL> insert into student values(2, ‘b’, 200);
SQL> savepoint s3;
SQL> insert into student values(3, ‘c’, 300);
SQL> savepoint s4;
SQL> insert into student values(4, ‘d’, 400);
Before rollback
SQL> select * from student;
NO NAME MARKS
--- ------- ----------
1 a 100
2 b 200
3 c 300
4 d 400
SQL> rollback to savepoint s3;
Or
SQL> rollback to s3;
This will rollback last two records.
SQL> select * from student;
NO NAME MARKS
--- ------- ----------
1 a 100
2 b 200
USING DCL
DCL commands are used to granting and revoking the permissions.
USING GRANT
This is used to grant the privileges to other users.
Syntax:
Grant
Ex:
SQL> grant select on student to sudha; -- you can give individual privilege
SQL> grant select, insert on student to sudha; -- you can give set of privileges
SQL> grant all on student to sudha; -- you can give all privileges
The sudha user has to use dot method to access the object.
SQL> select * from saketh.student;
The sudha user can not grant permission on student table to other users. To get this type of
option use the following.
SQL> grant all on student to sudha with grant option;
Now sudha user also grant permissions on student table.
USING REVOKE
This is used to revoke the privileges from the users to which you granted the privileges.
Syntax:
Revoke
Ex:
SQL> revoke select on student form sudha; -- you can revoke individual privilege
SQL> revoke select, insert on student from sudha; -- you can revoke set of privileges
SQL> revoke all on student from sudha; -- you can revoke all privileges
USING ALIASES
CREATE WITH SELECT
We can create a table using existing table [along with data].
Syntax:
Create table
Ex:
SQL> create table student1 as select * from student;
Creating table with your own column names.
SQL> create table student2(sno, sname, smarks) as select * from student;
Creating table with specified columns.
SQL> create table student3 as select no,name from student;
Creating table with out table data.
SQL> create table student2(sno, sname, smarks) as select * from student where 1 = 2;
In the above where clause give any condition which does not satisfy.
INSERT WITH SELECT
Using this we can insert existing table data to a another table in a single trip. But the table structure should be same.
Syntax:
Insert into
Ex:
SQL> insert into student1 select * from student;
Inserting data into specified columns
SQL> insert into student1(no, name) select no, name from student;
COLUMN ALIASES
Syntax:
Select
Ex:
SQL> select no sno from student;
or
SQL> select no “sno” from student;
TABLE ALIASES
If you are using table aliases you can use dot method to the columns.
Syntax:
Select
Ex:
SQL> select s.no, s.name from student s;
USING MERGE
MERGE
You can use merge command to perform insert and update in a single command.
Ex:
SQL> Merge into student1 s1
Using (select *From student2) s2
On(s1.no=s2.no)
When matched then
Update set marks = s2.marks
When not matched then
Insert (s1.no,s1.name,s1.marks)
Values(s2.no,s2.name,s2.marks);
In the above the two tables are with the same structure but we can merge different structured
tables also but the datatype of the columns should match.
Assume that student1 has columns like no,name,marks and student2 has columns like no,
name, hno, city.
SQL> Merge into student1 s1
Using (select *From student2) s2
On(s1.no=s2.no)
When matched then
Update set marks = s2.hno
When not matched then
Insert (s1.no,s1.name,s1.marks)
Values(s2.no,s2.name,s2.hno);
MULTIBLE INSERTS
We have table called DEPT with the following columns and data
DEPTNO DNAME LOC
-------- -------- ----
10 accounting new york
20 research dallas
30 sales Chicago
40 operations boston
a) CREATE STUDENT TABLE
SQL> Create table student(no number(2),name varchar(2),marks number(3));
b) MULTI INSERT WITH ALL FIELDS
SQL> Insert all
Into student values(1,’a’,100)
Into student values(2,’b’,200)
Into student values(3,’c’,300)
Select *from dept where deptno=10;
-- This inserts 3 rows
c) MULTI INSERT WITH SPECIFIED FIELDS
SQL> insert all
Into student (no,name) values(4,’d’)
Into student(name,marks) values(’e’,400)
Into student values(3,’c’,300)
Select *from dept where deptno=10;
-- This inserts 3 rows
d) MULTI INSERT WITH DUPLICATE ROWS
SQL> insert all
Into student values(1,’a’,100)
Into student values(2,’b’,200)
Into student values(3,’c’,300)
Select *from dept where deptno > 10;
-- This inserts 9 rows because in the select statement retrieves 3 records (3 inserts for each
row retrieved)
e) MULTI INSERT WITH CONDITIONS BASED
SQL> Insert all
When deptno > 10 then
Into student1 values(1,’a’,100)
When dname = ‘SALES’ then
Into student2 values(2,’b’,200)
When loc = ‘NEW YORK’ then
Into student3 values(3,’c’,300)
Select *from dept where deptno>10;
-- This inserts 4 rows because the first condition satisfied 3 times, second condition
satisfied once and the last none.
f) MULTI INSERT WITH CONDITIONS BASED AND ELSE
SQL> Insert all
When deptno > 100 then
Into student1 values(1,’a’,100)
When dname = ‘S’ then
Into student2 values(2,’b’,200)
When loc = ‘NEW YORK’ then
Into student3 values(3,’c’,300)
Else
Into student values(4,’d’,400)
Select *from dept where deptno>10;
-- This inserts 3 records because the else satisfied 3 times
g) MULTI INSERT WITH CONDITIONS BASED AND FIRST
SQL> Insert first
When deptno = 20 then
Into student1 values(1,’a’,100)
When dname = ‘RESEARCH’ then
Into student2 values(2,’b’,200)
When loc = ‘NEW YORK’ then
Into student3 values(3,’c’,300)
Select *from dept where deptno=20;
-- This inserts 1 record because the first clause avoid to check the remaining conditions
once the condition is satisfied.
h) MULTI INSERT WITH CONDITIONS BASED, FIRST AND ELSE
SQL> Insert first
When deptno = 30 then
Into student1 values(1,’a’,100)
When dname = ‘R’ then
Into student2 values(2,’b’,200)
When loc = ‘NEW YORK’ then
Into student3 values(3,’c’,300)
Else
Into student values(4,’d’,400)
Select *from dept where deptno=20;
-- This inserts 1 record because the else clause satisfied once
i) MULTI INSERT WITH MULTIBLE TABLES
SQL> Insert all
Into student1 values(1,’a’,100)
Into student2 values(2,’b’,200)
Into student3 values(3,’c’,300)
Select *from dept where deptno=10;
-- This inserts 3 rows
** You can use multi tables with specified fields, with duplicate rows, with conditions, with
first and else clauses.
FUNCTIONS
Functions can be categorized as follows.
Single row functions
Group functions
SINGLE ROW FUNCTIONS
Single row functions can be categorized into five. These will be applied for each row and produces individual output for each row.
Numeric functions
String functions
Date functions
Miscellaneous functions
Conversion functions
NUMERIC FUNCTIONS
Abs
Sign
Sqrt
Mod
Nvl
Power
Exp
Ln
Log
Ceil
Floor
Round
Trunk
Bitand
Greatest
Least
Coalesce
a) ABS
Absolute value is the measure of the magnitude of value.
Absolute value is always a positive number.
Syntax: abs (value)
Ex:
SQL> select abs(5), abs(-5), abs(0), abs(null) from dual;
ABS(5) ABS(-5) ABS(0) ABS(NULL)
---------- ---------- ---------- -------------
5 -5 0
b) SIGN
Sign gives the sign of a value.
Syntax: sign (value)
Ex:
SQL> select sign(5), sign(-5), sign(0), sign(null) from dual;
SIGN(5) SIGN(-5) SIGN(0) SIGN(NULL)
---------- ---------- ---------- --------------
1 -1 0
c) SQRT
This will give the square root of the given value.
Syntax: sqrt (value) -- here value must be positive.
Ex:
SQL> select sqrt(4), sqrt(0), sqrt(null), sqrt(1) from dual;
SQRT(4) SQRT(0) SQRT(NULL) SQRT(1)
---------- ---------- --------------- ----------
2 0 1
d) MOD
This will give the remainder.
Syntax: mod (value, divisor)
Ex:
SQL> select mod(7,4), mod(1,5), mod(null,null), mod(0,0), mod(-7,4) from dual;
MOD(7,4) MOD(1,5) MOD(NULL,NULL) MOD(0,0) MOD(-7,4)
------------ ---------- --------------------- ----------- -------------
3 1 0 -3
e) NVL
This will substitutes the specified value in the place of null values.
Syntax: nvl (null_col, replacement_value)
Ex:
SQL> select * from student; -- here for 3rd row marks value is null
NO NAME MARKS
--- ------- ---------
1 a 100
2 b 200
3 c
SQL> select no, name, nvl(marks,300) from student;
NO NAME NVL(MARKS,300)
--- ------- ---------------------
1 a 100
2 b 200
3 c 300
SQL> select nvl(1,2), nvl(2,3), nvl(4,3), nvl(5,4) from dual;
NVL(1,2) NVL(2,3) NVL(4,3) NVL(5,4)
---------- ---------- ---------- ----------
1 2 4 5
SQL> select nvl(0,0), nvl(1,1), nvl(null,null), nvl(4,4) from dual;
NVL(0,0) NVL(1,1) NVL(null,null) NVL(4,4)
---------- ---------- ----------------- ----------
0 1 4
f) POWER
Power is the ability to raise a value to a given exponent.
Syntax: power (value, exponent)
Ex:
SQL> select power(2,5), power(0,0), power(1,1), power(null,null), power(2,-5) from
dual;
POWER(2,5) POWER(0,0) POWER(1,1) POWER(NULL,NULL) POWER(2,-5)
-------------- -------------- ----- --------- ----------------------- ---------------
32 1 1 .03125
g) EXP
This will raise e value to the give power.
Syntax: exp (value)
Ex:
SQL> select exp(1), exp(2), exp(0), exp(null), exp(-2) from dual;
EXP(1) EXP(2) EXP(0) EXP(NULL) EXP(-2)
-------- --------- -------- ------------- ----------
2.71828183 7.3890561 1 .135335283
h) LN
This is based on natural or base e logarithm.
Syntax: ln (value) -- here value must be greater than zero which is positive only.
Ex:
SQL> select ln(1), ln(2), ln(null) from dual;
LN(1) LN(2) LN(NULL)
------- ------- ------------
0 .693147181
Ln and Exp are reciprocal to each other.
EXP (3) = 20.0855369
LN (20.0855369) = 3
i) LOG
This is based on 10 based logarithm.
Syntax: log (10, value) -- here value must be greater than zero which is positive only.
Ex:
SQL> select log(10,100), log(10,2), log(10,1), log(10,null) from dual;
LOG(10,100) LOG(10,2) LOG(10,1) LOG(10,NULL)
--------------- ----------- ------------ -----------------
2 .301029996 0
LN (value) = LOG (EXP(1), value)
SQL> select ln(3), log(exp(1),3) from dual;
LN(3) LOG(EXP(1),3)
------- -----------------
1.09861229 1.09861229
j) CEIL
This will produce a whole number that is greater than or equal to the specified value.
Syntax: ceil (value)
Ex:
SQL> select ceil(5), ceil(5.1), ceil(-5), ceil( -5.1), ceil(0), ceil(null) from dual;
CEIL(5) CEIL(5.1) CEIL(-5) CEIL(-5.1) CEIL(0) CEIL(NULL)
--------- ----------- ---------- ------------ -------- --------------
5 6 -5 -5 0
k) FLOOR
This will produce a whole number that is less than or equal to the specified value.
Syntax: floor (value)
Ex:
SQL> select floor(5), floor(5.1), floor(-5), floor( -5.1), floor(0), floor(null) from dual;
FLOOR(5) FLOOR(5.1) FLOOR(-5) FLOOR(-5.1) FLOOR(0) FLOOR(NULL)
----------- ------------- ------------ -------------- ----------- ----------------
5 5 -5 -6 0
l) ROUND
This will rounds numbers to a given number of digits of precision.
Syntax: round (value, precision)
Ex:
SQL> select round(123.2345), round(123.2345,2), round(123.2354,2) from dual;
ROUND(123.2345) ROUND(123.2345,0) ROUND(123.2345,2) ROUND(123.2354,2)
--------------------- ------------------------ ----------------------- -----------------------
123 123 123.23 123.24
SQL> select round(123.2345,-1), round(123.2345,-2), round(123.2345,-3),
round(123.2345,-4) from dual;
ROUND(123.2345,-1) ROUND(123.2345,-2) ROUND(123.2345,-3) ROUND(123.2345,-4)
------------------------ ------------------------- ------------------------ ------------------------
120 100 0 0
SQL> select round(123,0), round(123,1), round(123,2) from dual;
ROUND(123,0) ROUND(123,1) ROUND(123,2)
----------------- ----------------- ----------------
123 123 123
SQL> select round(-123,0), round(-123,1), round(-123,2) from dual;
ROUND(-123,0) ROUND(-123,1) ROUND(-123,2)
------------------ ----------------- -------------------
-123 -123 -123
SQL> select round(123,-1), round(123,-2), round(123,-3), round(-123,-1), round(-123,-
2), round(-123,-3) from dual;
ROUND(123,-1) ROUND(123,-2) ROUND(123,-3) ROUND(-123,-1) ROUND(-123,-2)
ROUND(-123,-3)
------------- ------------- ------------- -------------- -------------- --------------
120 100 0 -120 -100 0
SQL> select round(null,null), round(0,0), round(1,1), round(-1,-1), round(-2,-2) from
dual;
ROUND(NULL,NULL) ROUND(0,0) ROUND(1,1) ROUND(-1,-1) ROUND(-2,-2)
----------------------- -------------- -------------- ---------------- ----------------
0 1 0 0
m) TRUNC
This will truncates or chops off digits of precision from a number.
Syntax: trunc (value, precision)
Ex:
SQL> select trunc(123.2345), trunc(123.2345,2), trunc(123.2354,2) from dual;
TRUNC(123.2345) TRUNC(123.2345,2) TRUNC(123.2354,2)
--------------------- ----------------------- -----------------------
123 123.23 123.23
SQL> select trunc(123.2345,-1), trunc(123.2345,-2), trunc(123.2345,-3),
trunc(123.2345,-4) from dual;
TRUNC(123.2345,-1) TRUNC(123.2345,-2) TRUNC(123.2345,-3) TRUNC(123.2345,-4)
------------------------ ------------------------ ----------------------- ------------------------
120 100 0 0
SQL> select trunc(123,0), trunc(123,1), trunc(123,2) from dual;
TRUNC(123,0) TRUNC(123,1) TRUNC(123,2)
---------------- ---------------- -----------------
123 123 123
SQL> select trunc(-123,0), trunc(-123,1), trunc(-123,2) from dual;
TRUNC(-123,0) TRUNC(-123,1) TRUNC(-123,2)
----------------- ----------------- -----------------
-123 -123 -123
SQL> select trunc(123,-1), trunc(123,-2), trunc(123,-3), trunc(-123,-1), trunc(-123,2),
trunc(-123,-3) from dual;
TRUNC(123,-1) TRUNC(123,-2) TRUNC(123,-3) TRUNC(-123,-1) TRUNC(-123,2) TRUNC(-
123,-3)
------------- ------------- ------------- -------------- ------------- --------------
120 100 0 -120 -123 0
SQL> select trunc(null,null), trunc(0,0), trunc(1,1), trunc(-1,-1), trunc(-2,-2) from dual;
TRUNC(NULL,NULL) TRUNC(0,0) TRUNC(1,1) TRUNC(-1,-1) TRUNC(-2,-2)
----------------------- ------------- ------------- --------------- ----------------
0 1 0 0
n) BITAND
This will perform bitwise and operation.
Syntax: bitand (value1, value2)
Ex:
SQL> select bitand(2,3), bitand(0,0), bitand(1,1), bitand(null,null), bitand(-2,-3) from
dual;
BITAND(2,3) BITAND(0,0) BITAND(1,1) BITAND(NULL,NULL) BITAND(-2,-3)
-------------- --------------- -------------- ------------------------ -----------------
2 0 1 -4
o) GREATEST
This will give the greatest number.
Syntax: greatest (value1, value2, value3 … valuen)
Ex:
SQL> select greatest(1, 2, 3), greatest(-1, -2, -3) from dual;
GREATEST(1,2,3) GREATEST(-1,-2,-3)
-------------------- -----------------------
3 -1
If all the values are zeros then it will display zero.
If all the parameters are nulls then it will display nothing.
If any of the parameters is null it will display nothing.
p) LEAST
This will give the least number.
Syntax: least (value1, value2, value3 … valuen)
Ex:
SQL> select least(1, 2, 3), least(-1, -2, -3) from dual;
LEAST(1,2,3) LEAST(-1,-2,-3)
-------------------- -----------------------
1 -3
If all the values are zeros then it will display zero.
If all the parameters are nulls then it will display nothing.
If any of the parameters is null it will display nothing.
q) COALESCE
This will return first non-null value.
Syntax: coalesce (value1, value2, value3 … valuen)
Ex:
SQL> select coalesce(1,2,3), coalesce(null,2,null,5) from dual;
COALESCE(1,2,3) COALESCE(NULL,2,NULL,5)
------------------- -------------------------------
1 2
STRING FUNCTIONS
Initcap
Upper
Lower
Length
Rpad
Lpad
Ltrim
Rtrim
Trim
Translate
Replace
Soundex
Concat ( ‘ || ‘ Concatenation operator)
Ascii
Chr
Substr
Instr
Decode
Greatest
Least
Coalesce
a) INITCAP
This will capitalize the initial letter of the string.
Syntax: initcap (string)
Ex:
SQL> select initcap('computer') from dual;
INITCAP
-----------
Computer
b) UPPER
This will convert the string into uppercase.
Syntax: upper (string)
Ex:
SQL> select upper('computer') from dual;
UPPER
-----------
COMPUTER
c) LOWER
This will convert the string into lowercase.
Syntax: lower (string)
Ex:
SQL> select lower('COMPUTER') from dual;
LOWER
-----------
computer
d) LENGTH
This will give length of the string.
Syntax: length (string)
Ex:
SQL> select length('computer') from dual;
LENGTH
-----------
8
e) RPAD
This will allows you to pad the right side of a column with any set of characters.
Syntax: rpad (string, length [, padding_char])
Ex:
SQL> select rpad('computer',15,'*'), rpad('computer',15,'*#') from dual;
RPAD('COMPUTER' RPAD('COMPUTER'
---------------------- ----------------------
computer******* computer*#*#*#*
-- Default padding character was blank space.
f) LPAD
This will allows you to pad the left side of a column with any set of characters.
Syntax: lpad (string, length [, padding_char])
Ex:
SQL> select lpad('computer',15,'*'), lpad('computer',15,'*#') from dual;
LPAD('COMPUTER' LPAD('COMPUTER'
--------------------- ---------------------
*******computer *#*#*#*computer
-- Default padding character was blank space.
g) LTRIM
This will trim off unwanted characters from the left end of string.
Syntax: ltrim (string [,unwanted_chars])
Ex:
SQL> select ltrim('computer','co'), ltrim('computer','com') from dual;
LTRIM( LTRIM
-------- ---------
mputer puter
SQL> select ltrim('computer','puter'), ltrim('computer','omputer') from dual;
LTRIM('C LTRIM('C
---------- ----------
computer computer
-- If you haven’t specify any unwanted characters it will display entire string.
h) RTRIM
This will trim off unwanted characters from the right end of string.
Syntax: rtrim (string [, unwanted_chars])
Ex:
SQL> select rtrim('computer','er'), rtrim('computer','ter') from dual;
RTRIM( RTRIM
-------- ---------
comput compu
SQL> select rtrim('computer','comput’), rtrim('computer','compute') from dual;
RTRIM('C RTRIM('C
---------- ----------
computer computer
-- If you haven’t specify any unwanted characters it will display entire string.
i) TRIM
This will trim off unwanted characters from the both sides of string.
Syntax: trim (unwanted_chars from string)
Ex:
SQL> select trim( 'i' from 'indiani') from dual;
TRIM(
-----
ndian
SQL> select trim( leading'i' from 'indiani') from dual; -- this will work as LTRIM
TRIM(L
------
ndiani
SQL> select trim( trailing'i' from 'indiani') from dual; -- this will work as RTRIM
TRIM(T
------
Indian
j) TRANSLATE
This will replace the set of characters, character by character.
Syntax: translate (string, old_chars, new_chars)
Ex:
SQL> select translate('india','in','xy') from dual;
TRANS
--------
xydxa
k) REPLACE
This will replace the set of characters, string by string.
Syntax: replace (string, old_chars [, new_chars])
Ex:
SQL> select replace('india','in','xy'), replace(‘india’,’in’) from dual;
REPLACE REPLACE
----------- -----------
Xydia dia
l) SOUNDEX
This will be used to find words that sound like other words, exclusively used in where clause.
Syntax: soundex (string)
Ex:
SQL> select * from emp where soundex(ename) = soundex('SMIT');
EMPNO ENAME JOB MGR HIREDATE SAL DEPTNO
-------- -------- ----- ----- ------------ --------- ----------
7369 SMITH CLERK 7902 17-DEC-80 500 20
m) CONCAT
This will be used to combine two strings only.
Syntax: concat (string1, string2)
Ex:
SQL> select concat('computer',' operator') from dual;
CONCAT('COMPUTER'
-------------------------
computer operator
If you want to combine more than two strings you have to use concatenation operator (||).
SQL> select 'how' || ' are' || ' you' from dual;
'HOW'||'ARE
---------------
how are you
n) ASCII
This will return the decimal representation in the database character set of the first
character of the string.
Syntax: ascii (string)
Ex:
SQL> select ascii('a'), ascii('apple') from dual;
ASCII('A') ASCII('APPLE')
------------ ------------------
97 97
o) CHR
This will return the character having the binary equivalent to the string in either the
database character set or the national character set.
Syntax: chr (number)
Ex:
SQL> select chr(97) from dual;
CHR
-----
a
p) SUBSTR
This will be used to extract substrings.
Syntax: substr (string, start_chr_count [, no_of_chars])
Ex:
SQL> select substr('computer',2), substr('computer',2,5), substr('computer',3,7) from
dual;
SUBSTR( SUBST SUBSTR
---------- ------- --------
omputer omput mputer
If no_of_chars parameter is negative then it will display nothing.
If both parameters except string are null or zeros then it will display nothing.
If no_of_chars parameter is greater than the length of the string then it ignores and calculates based on the orginal string length.
If start_chr_count is negative then it will extract the substring from right end.
1 2 3 4 5 6 7 8
C O M P U T E R
-8 -7 -6 -5 -4 -3 -2 -1
q) INSTR
This will allows you for searching through a string for set of characters.
Syntax: instr (string, search_str [, start_chr_count [, occurrence] ])
Ex:
SQL> select instr('information','o',4,1), instr('information','o',4,2) from dual;
INSTR('INFORMATION','O',4,1) INSTR('INFORMATION','O',4,2)
------------------------------------ -------------------------------------
4 10
If you are not specifying start_chr_count and occurrence then it will start search from
the beginning and finds first occurrence only.
If both parameters start_chr_count and occurrence are null, it will display nothing.
r) DECODE
Decode will act as value by value substitution.
For every value of field, it will checks for a match in a series of if/then tests.
Syntax: decode (value, if1, then1, if2, then2, ……. else);
Ex:
SQL> select sal, decode(sal,500,'Low',5000,'High','Medium') from emp;
SAL DECODE
----- ---------
500 Low
2500 Medium
2000 Medium
3500 Medium
3000 Medium
5000 High
4000 Medium
5000 High
1800 Medium
1200 Medium
2000 Medium
2700 Medium
2200 Medium
3200 Medium
SQL> select decode(1,1,3), decode(1,2,3,4,4,6) from dual;
DECODE(1,1,3) DECODE(1,2,3,4,4,6)
----------------- ------------------------
3 6
If the number of parameters are odd and different then decode will display nothing.
If the number of parameters are even and different then decode will display last
value.
If all the parameters are null then decode will display nothing.
If all the parameters are zeros then decode will display zero.
s) GREATEST
This will give the greatest string.
Syntax: greatest (strng1, string2, string3 … stringn)
Ex:
SQL> select greatest('a', 'b', 'c'), greatest('satish','srinu','saketh') from dual;
GREAT GREAT
------- -------
c srinu
If all the parameters are nulls then it will display nothing.
If any of the parameters is null it will display nothing.
t) LEAST
This will give the least string.
Syntax: greatest (strng1, string2, string3 … stringn)
Ex:
SQL> select least('a', 'b', 'c'), least('satish','srinu','saketh') from dual;
LEAST LEAST
------- -------
a saketh
If all the parameters are nulls then it will display nothing.
If any of the parameters is null it will display nothing.
u) COALESCE
This will gives the first non-null string.
Syntax: coalesce (strng1, string2, string3 … stringn)
Ex:
SQL> select coalesce('a','b','c'), coalesce(null,'a',null,'b') from dual;
COALESCE COALESCE
----------- -----------
a a
DATE FUNCTIONS
Sysdate
Current_date
Current_timestamp
Systimestamp
Localtimestamp
Dbtimezone
Sessiontimezone
To_char
To_date
Add_months
Months_between
Next_day
Last_day
Extract
Greatest
Least
Round
Trunc
New_time
Coalesce
Oracle default date format is DD-MON-YY.
We can change the default format to our desired format by using the following command.
SQL> alter session set nls_date_format = ‘DD-MONTH-YYYY’;
But this will expire once the session was closed.
a) SYSDATE
This will give the current date and time.
Ex:
SQL> select sysdate from dual;
SYSDATE
-----------
24-DEC-06
b) CURRENT_DATE
This will returns the current date in the session’s timezone.
Ex:
SQL> select current_date from dual;
CURRENT_DATE
------------------
24-DEC-06
c) CURRENT_TIMESTAMP
This will returns the current timestamp with the active time zone information.
Ex:
SQL> select current_timestamp from dual;
CURRENT_TIMESTAMP
---------------------------------------------------------------------------
24-DEC-06 03.42.41.383369 AM +05:30
d) SYSTIMESTAMP
This will returns the system date, including fractional seconds and time zone of the
database.
Ex:
SQL> select systimestamp from dual;
SYSTIMESTAMP
---------------------------------------------------------------------------
24-DEC-06 03.49.31.830099 AM +05:30
e) LOCALTIMESTAMP
This will returns local timestamp in the active time zone information, with no time zone
information shown.
Ex:
SQL> select localtimestamp from dual;
LOCALTIMESTAMP
---------------------------------------------------------------------------
24-DEC-06 03.44.18.502874 AM
f) DBTIMEZONE
This will returns the current database time zone in UTC format. (Coordinated Universal Time)
Ex:
SQL> select dbtimezone from dual;
DBTIMEZONE
---------------
-07:00
g) SESSIONTIMEZONE
This will returns the value of the current session’s time zone.
Ex:
SQL> select sessiontimezone from dual;
SESSIONTIMEZONE
---------------------------------------------------------------------------
+05:30
h) TO_CHAR
This will be used to extract various date formats.
The available date formats as follows.
Syntax: to_char (date, format)
DATE FORMATS
D -- No of days in week
DD -- No of days in month
DDD -- No of days in year
MM -- No of month
MON -- Three letter abbreviation of month
MONTH -- Fully spelled out month
RM -- Roman numeral month
DY -- Three letter abbreviated day
DAY -- Fully spelled out day
Y -- Last one digit of the year
YY -- Last two digits of the year
YYY -- Last three digits of the year
YYYY -- Full four digit year
SYYYY -- Signed year
I -- One digit year from ISO standard
IY -- Two digit year from ISO standard
IYY -- Three digit year from ISO standard
IYYY -- Four digit year from ISO standard
Y, YYY -- Year with comma
YEAR -- Fully spelled out year
CC -- Century
Q -- No of quarters
W -- No of weeks in month
WW -- No of weeks in year
IW -- No of weeks in year from ISO standard
HH -- Hours
MI -- Minutes
SS -- Seconds
FF -- Fractional seconds
AM or PM -- Displays AM or PM depending upon time of day
A.M or P.M -- Displays A.M or P.M depending upon time of day
AD or BC -- Displays AD or BC depending upon the date
A.D or B.C -- Displays AD or BC depending upon the date
FM -- Prefix to month or day, suppresses padding of month or day
TH -- Suffix to a number
SP -- suffix to a number to be spelled out
SPTH -- Suffix combination of TH and SP to be both spelled out
THSP -- same as SPTH
Ex:
SQL> select to_char(sysdate,'dd month yyyy hh:mi:ss am dy') from dual;
TO_CHAR(SYSDATE,'DD MONTH YYYYHH:MI
----------------------------------------------------
24 december 2006 02:03:23 pm sun
SQL> select to_char(sysdate,'dd month year') from dual;
TO_CHAR(SYSDATE,'DDMONTHYEAR')
-------------------------------------------------------
24 december two thousand six
SQL> select to_char(sysdate,'dd fmmonth year') from dual;
TO_CHAR(SYSDATE,'DD FMMONTH YEAR')
-------------------------------------------------------
24 december two thousand six
SQL> select to_char(sysdate,'ddth DDTH') from dual;
TO_CHAR(S
------------
24th 24TH
SQL> select to_char(sysdate,'ddspth DDSPTH') from dual;
TO_CHAR(SYSDATE,'DDSPTHDDSPTH
------------------------------------------
twenty-fourth TWENTY-FOURTH
SQL> select to_char(sysdate,'ddsp Ddsp DDSP ') from dual;
TO_CHAR(SYSDATE,'DDSPDDSPDDSP')
------------------------------------------------
twenty-four Twenty-Four TWENTY-FOUR
i) TO_DATE
This will be used to convert the string into data format.
Syntax: to_date (date)
Ex:
SQL> select to_char(to_date('24/dec/2006','dd/mon/yyyy'), 'dd * month * day') from
dual;
TO_CHAR(TO_DATE('24/DEC/20
--------------------------
24 * december * Sunday
-- If you are not using to_char oracle will display output in default date format.
j) ADD_MONTHS
This will add the specified months to the given date.
Syntax: add_months (date, no_of_months)
Ex:
SQL> select add_months(to_date('11-jan-1990','dd-mon-yyyy'), 5) from dual;
ADD_MONTHS
----------------
11-JUN-90
SQL> select add_months(to_date('11-jan-1990','dd-mon-yyyy'), -5) from dual;
ADD_MONTH
---------------
11-AUG-89
If no_of_months is zero then it will display the same date.
If no_of_months is null then it will display nothing.
k) MONTHS_BETWEEN
This will give difference of months between two dates.
Syntax: months_between (date1, date2)
Ex:
SQL> select months_between(to_date('11-aug-1990','dd-mon-yyyy'), to_date('11-jan-
1990','dd-mon-yyyy')) from dual;
MONTHS_BETWEEN(TO_DATE('11-AUG-1990','DD-MON-YYYY'),TO_DATE('11-JAN-1990','DD-MON-YYYY'))
-----------------------------------------------------------------------------------------------
7
SQL> select months_between(to_date('11-jan-1990','dd-mon-yyyy'), to_date('11-aug-
1990','dd-mon-yyyy')) from dual;
MONTHS_BETWEEN(TO_DATE('11-JAN-1990','DD-MON-YYYY'),TO_DATE('11-AUG-1990','DD-MON-YYYY'))
-------------------------------------------------------------------------------------------------
-7
l) NEXT_DAY
This will produce next day of the given day from the specified date.
Syntax: next_day (date, day)
Ex:
SQL> select next_day(to_date('24-dec-2006','dd-mon-yyyy'),'sun') from dual;
NEXT_DAY(
-------------
31-DEC-06
-- If the day parameter is null then it will display nothing.
m) LAST_DAY
This will produce last day of the given date.
Syntax: last_day (date)
Ex:
SQL> select last_day(to_date('24-dec-2006','dd-mon-yyyy'),'sun') from dual;
LAST_DAY(
-------------
31-DEC-06
n) EXTRACT
This is used to extract a portion of the date value.
Syntax: extract ((year | month | day | hour | minute | second), date)
Ex:
SQL> select extract(year from sysdate) from dual;
EXTRACT(YEARFROMSYSDATE)
------------------------------------
2006
-- You can extract only one value at a time.
o) GREATEST
This will give the greatest date.
Syntax: greatest (date1, date2, date3 … daten)
Ex:
SQL> select greatest(to_date('11-jan-90','dd-mon-yy'),to_date('11-mar-90','dd-mon-
yy'),to_date('11-apr-90','dd-mon-yy')) from dual;
GREATEST(
-------------
11-APR-90
p) LEAST
This will give the least date.
Syntax: least (date1, date2, date3 … daten)
Ex:
SQL> select least(to_date('11-jan-90','dd-mon-yy'),to_date('11-mar-90','dd-mon-
yy'),to_date('11-apr-90','dd-mon-yy')) from dual;
LEAST(
-------------
11-JAN-90
q) ROUND
Round will rounds the date to which it was equal to or greater than the given date.
Syntax: round (date, (day | month | year))
If the second parameter was year then round will checks the month of the given date in the
following ranges.
JAN -- JUN
JUL -- DEC
If the month falls between JAN and JUN then it returns the first day of the current year.
If the month falls between JUL and DEC then it returns the first day of the next year.
If the second parameter was month then round will checks the day of the given date in the
following ranges.
1 -- 15
16 -- 31
If the day falls between 1 and 15 then it returns the first day of the current month.
If the day falls between 16 and 31 then it returns the first day of the next month.
If the second parameter was day then round will checks the week day of the given date in
the following ranges.
SUN -- WED
THU -- SUN
If the week day falls between SUN and WED then it returns the previous sunday.
If the weekday falls between THU and SUN then it returns the next sunday.
If the second parameter was null then it returns nothing.
If the you are not specifying the second parameter then round will resets the time to the
begining of the current day in case of user specified date.
If the you are not specifying the second parameter then round will resets the time to the
begining of the next day in case of sysdate.
Ex:
SQL> select round(to_date('24-dec-04','dd-mon-yy'),'year'), round(to_date('11-mar-
06','dd-mon-yy'),'year') from dual;
ROUND(TO_ ROUND(TO_
------------ ---------------
01-JAN-05 01-JAN-06
SQL> select round(to_date('11-jan-04','dd-mon-yy'),'month'), round(to_date('18-jan-
04','dd-mon-yy'),'month') from dual;
ROUND(TO_ ROUND(TO_
------------- ---------------
01-JAN-04 01-FEB-04
SQL> select round(to_date('26-dec-06','dd-mon-yy'),'day'), round(to_date('29-dec-
06','dd-mon-yy'),'day') from dual;
ROUND(TO_ ROUND(TO_
-------------- --------------
24-DEC-06 31-DEC-06
SQL> select to_char(round(to_date('24-dec-06','dd-mon-yy')), 'dd mon yyyy hh:mi:ss am')
from dual;
TO_CHAR(ROUND(TO_DATE('
---------------------------------
24 dec 2006 12:00:00 am
r) TRUNC
Trunc will chops off the date to which it was equal to or less than the given date.
Syntax: trunc (date, (day | month | year))
If the second parameter was year then it always returns the first day of the current year.
If the second parameter was month then it always returns the first day of the current month.
If the second parameter was day then it always returns the previous sunday.
If the second parameter was null then it returns nothing.
If the you are not specifying the second parameter then trunk will resets the time to the
begining of the current day.
Ex:
SQL> select trunc(to_date('24-dec-04','dd-mon-yy'),'year'), trunc(to_date('11-mar-
06','dd-mon-yy'),'year') from dual;
TRUNC(TO_ TRUNC(TO_
------------- --------------
01-JAN-04 01-JAN-06
SQL> select trunc(to_date('11-jan-04','dd-mon-yy'),'month'), trunc(to_date('18-jan-
04','dd-mon-yy'),'month') from dual;
TRUNC(TO_ TRUNC(TO_
------------- -------------
01-JAN-04 01-JAN-04
SQL> select trunc(to_date('26-dec-06','dd-mon-yy'),'day'), trunc(to_date('29-dec-06','dd-
mon-yy'),'day') from dual;
TRUNC(TO_ TRUNC(TO_
------------- --------------
24-DEC-06 24-DEC-06
SQL> select to_char(trunc(to_date('24-dec-06','dd-mon-yy')), 'dd mon yyyy hh:mi:ss am')
from dual;
TO_CHAR(TRUNC(TO_DATE('
---------------------------------
24 dec 2006 12:00:00 am
s) NEW_TIME
This will give the desired timezone’s date and time.
Syntax: new_time (date, current_timezone, desired_timezone)
Available timezones are as follows.
TIMEZONES
AST/ADT -- Atlantic standard/day light time
BST/BDT -- Bering standard/day light time
CST/CDT -- Central standard/day light time
EST/EDT -- Eastern standard/day light time
GMT -- Greenwich mean time
HST/HDT -- Alaska-Hawaii standard/day light time
MST/MDT -- Mountain standard/day light time
NST -- Newfoundland standard time
PST/PDT -- Pacific standard/day light time
YST/YDT -- Yukon standard/day light time
Ex:
SQL> select to_char(new_time(sysdate,'gmt','yst'),'dd mon yyyy hh:mi:ss am') from dual;
TO_CHAR(NEW_TIME(SYSDAT
-----------------------------------
24 dec 2006 02:51:20 pm
SQL> select to_char(new_time(sysdate,'gmt','est'),'dd mon yyyy hh:mi:ss am') from dual;
TO_CHAR(NEW_TIME(SYSDAT
-----------------------
24 dec 2006 06:51:26 pm
t) COALESCE
This will give the first non-null date.
Syntax: coalesce (date1, date2, date3 … daten)
Ex:
SQL> select coalesce('12-jan-90','13-jan-99'), coalesce(null,'12-jan-90','23-mar-98',null)
from dual;
COALESCE( COALESCE(
------------- ------------
12-jan-90 12-jan-90
MISCELLANEOUS FUNCTIONS
Uid
User
Vsize
Rank
Dense_rank
a) UID
This will returns the integer value corresponding to the user currently logged in.
Ex:
SQL> select uid from dual;
UID
----------
319
b) USER
This will returns the login’s user name.
Ex:
SQL> select user from dual;
USER
----------------
SAKETH
c) VSIZE
This will returns the number of bytes in the expression.
Ex:
SQL> select vsize(123), vsize('computer'), vsize('12-jan-90') from dual;
VSIZE(123) VSIZE('COMPUTER') VSIZE('12-JAN-90')
------------- ----------------------- ----------------------
3 8 9
d) RANK
This will give the non-sequential ranking.
Ex:
SQL> select rownum,sal from (select sal from emp order by sal desc);
ROWNUM SAL
---------- ----------
1 5000
2 3000
3 3000
4 2975
5 2850
6 2450
7 1600
8 1500
9 1300
10 1250
11 1250
12 1100
13 1000
14 950
15 800
SQL> select rank(2975) within group(order by sal desc) from emp;
RANK(2975)WITHINGROUP(ORDERBYSALDESC)
---------------------------------------------------------
4
d) DENSE_RANK
This will give the sequential ranking.
Ex:
SQL> select dense_rank(2975) within group(order by sal desc) from emp;
DENSE_RANK(2975)WITHINGROUP(ORDERBYSALDESC)
-----------------------------------------------------------------
3
CONVERSION FUNCTIONS
Bin_to_num
Chartorowid
Rowidtochar
To_number
To_char
To_date
a) BIN_TO_NUM
This will convert the binary value to its numerical equivalent.
Syntax: bin_to_num( binary_bits)
Ex:
SQL> select bin_to_num(1,1,0) from dual;
BIN_TO_NUM(1,1,0)
------------------------
6
If all the bits are zero then it produces zero.
If all the bits are null then it produces an error.
b) CHARTOROWID
This will convert a character string to act like an internal oracle row identifier or rowid.
c) ROWIDTOCHAR
This will convert an internal oracle row identifier or rowid to character string.
d) TO_NUMBER
This will convert a char or varchar to number.
e) TO_CHAR
This will convert a number or date to character string.
f) TO_DATE
This will convert a number, char or varchar to a date.
GROUP FUNCTIONS
Sum
Avg
Max
Min
Count
Group functions will be applied on all the rows but produces single output.
a) SUM
This will give the sum of the values of the specified column.
Syntax: sum (column)
Ex:
SQL> select sum(sal) from emp;
SUM(SAL)
----------
38600
b) AVG
This will give the average of the values of the specified column.
Syntax: avg (column)
Ex:
SQL> select avg(sal) from emp;
AVG(SAL)
---------------
2757.14286
c) MAX
This will give the maximum of the values of the specified column.
Syntax: max (column)
Ex:
SQL> select max(sal) from emp;
MAX(SAL)
----------
5000
d) MIN
This will give the minimum of the values of the specified column.
Syntax: min (column)
Ex:
SQL> select min(sal) from emp;
MIN(SAL)
----------
500
e) COUNT
This will give the count of the values of the specified column.
Syntax: count (column)
Ex:
SQL> select count(sal),count(*) from emp;
COUNT(SAL) COUNT(*)
-------------- ------------
14 14
CONSTRAINTS
Constraints are categorized as follows.
Domain integrity constraints
Not null
Check
Entity integrity constraints
Unique
Primary key
Referential integrity constraints
Foreign key
Constraints are always attached to a column not a table.
We can add constraints in three ways.
Column level -- along with the column definition
Table level -- after the table definition
Alter level -- using alter command
While adding constraints you need not specify the name but the type only, oracle will internally name the constraint.
If you want to give a name to the constraint, you have to use the constraint clause.
NOT NULL
This is used to avoid null values.
We can add this constraint in column level only.
Ex:
SQL> create table student(no number(2) not null, name varchar(10), marks number(3));
SQL> create table student(no number(2) constraint nn not null, name varchar(10), marks
number(3));
CHECK
This is used to insert the values based on specified condition.
We can add this constraint in all three levels.
Ex:
COLUMN LEVEL
SQL> create table student(no number(2) , name varchar(10), marks number(3) check
(marks > 300));
SQL> create table student(no number(2) , name varchar(10), marks number(3) constraint ch
check(marks > 300));
TABLE LEVEL
SQL> create table student(no number(2) , name varchar(10), marks number(3), check
(marks > 300));
SQL> create table student(no number(2) , name varchar(10), marks number(3), constraint
ch check(marks > 300));
ALTER LEVEL
SQL> alter table student add check(marks>300);
SQL> alter table student add constraint ch check(marks>300);
UNIQUE
This is used to avoid duplicates but it allow nulls.
We can add this constraint in all three levels.
Ex:
COLUMN LEVEL
SQL> create table student(no number(2) unique, name varchar(10), marks number(3));
SQL> create table student(no number(2) constraint un unique, name varchar(10), marks
number(3));
TABLE LEVEL
SQL> create table student(no number(2) , name varchar(10), marks number(3),
unique(no));
SQL> create table student(no number(2) , name varchar(10), marks number(3), constraint
un unique(no));
ALTER LEVEL
SQL> alter table student add unique(no);
SQL> alter table student add constraint un unique(no);
PRIMARY KEY
This is used to avoid duplicates and nulls. This will work as combination of unique and not null.
Primary key always attached to the parent table.
We can add this constraint in all three levels.
Ex:
COLUMN LEVEL
SQL> create table student(no number(2) primary key, name varchar(10), marks number(3));
SQL> create table student(no number(2) constraint pk primary key, name varchar(10),
marks number(3));
TABLE LEVEL
SQL> create table student(no number(2) , name varchar(10), marks number(3),
primary key(no));
SQL> create table student(no number(2) , name varchar(10), marks number(3), constraint
pk primary key(no));
ALTER LEVEL
SQL> alter table student add primary key(no);
SQL> alter table student add constraint pk primary key(no);
FOREIGN KEY
This is used to reference the parent table primary key column which allows duplicates.
Foreign key always attached to the child table.
We can add this constraint in table and alter levels only.
Ex:
TABLE LEVEL
SQL> create table emp(empno number(2), ename varchar(10), deptno number(2),
primary key(empno), foreign key(deptno) references dept(deptno));
SQL> create table emp(empno number(2), ename varchar(10), deptno number(2),
constraint pk primary key(empno), constraint fk foreign key(deptno) references
dept(deptno));
ALTER LEVEL
SQL> alter table emp add foreign key(deptno) references dept(deptno);
SQL> alter table emp add constraint fk foreign key(deptno) references dept(deptno);
Once the primary key and foreign key relationship has been created then you can not remove any parent record if the dependent childs exists.
USING ON DELTE CASCADE
By using this clause you can remove the parent record even it childs exists.
Because when ever you remove parent record oracle automatically removes all its dependent records from child table, if this clause is present while creating foreign key constraint.
Ex:
TABLE LEVEL
SQL> create table emp(empno number(2), ename varchar(10), deptno number(2),
primary key(empno), foreign key(deptno) references dept(deptno) on delete cascade);
SQL> create table emp(empno number(2), ename varchar(10), deptno number(2),
constraint pk primary key(empno), constraint fk foreign key(deptno) references
dept(deptno) on delete cascade);
ALTER LEVEL
SQL> alter table emp add foreign key(deptno) references dept(deptno) on delete cascade;
SQL> alter table emp add constraint fk foreign key(deptno) references dept(deptno) on
delete cascade;
COMPOSITE KEYS
A composite key can be defined on a combination of columns.
We can define composite keys on entity integrity and referential integrity constraints.
Composite key can be defined in table and alter levels only.
Ex:
UNIQUE (TABLE LEVEL)
SQL> create table student(no number(2) , name varchar(10), marks number(3),
unique(no,name));
SQL> create table student(no number(2) , name varchar(10), marks number(3), constraint
un unique(no,name));
UNIQUE (ALTER LEVEL)
SQL> alter table student add unique(no,name);
SQL> alter table student add constraint un unique(no,name);
PRIMARY KEY (TABLE LEVEL)
SQL> create table student(no number(2) , name varchar(10), marks number(3),
primary key(no,name));
SQL> create table student(no number(2) , name varchar(10), marks number(3), constraint
pk primary key(no,name));
PRIMARY KEY (ALTER LEVEL)
SQL> alter table student add primary key(no,anme);
SQL> alter table student add constraint pk primary key(no,name);
FOREIGN KEY (TABLE LEVEL)
SQL> create table emp(empno number(2), ename varchar(10), deptno number(2), dname
varchar(10), primary key(empno), foreign key(deptno,dname) references
dept(deptno,dname));
SQL> create table emp(empno number(2), ename varchar(10), deptno number(2), dname
varchar(10), constraint pk primary key(empno), constraint fk foreign
key(deptno,dname) references dept(deptno,dname));
FOREIGN KEY (ALTER LEVEL)
SQL> alter table emp add foreign key(deptno,dname) references dept(deptno,dname);
SQL> alter table emp add constraint fk foreign key(deptno,dname) references
dept(deptno,dname);
DEFERRABLE CONSTRAINTS
Each constraint has two additional attributes to support deferred checking of constraints.
Deferred initially immediate
Deferred initially deferred
Deferred initially immediate checks for constraint violation at the time of insert.
Deferred initially deferred checks for constraint violation at the time of commit.
Ex:
SQL> create table student(no number(2), name varchar(10), marks number(3), constraint
un unique(no) deferred initially immediate);
SQL> create table student(no number(2), name varchar(10), marks number(3), constraint
un unique(no) deferred initially deferred);
SQL> alter table student add constraint un unique(no) deferrable initially deferred;
SQL> set constraints all immediate;
This will enable all the constraints violations at the time of inserting.
SQL> set constraints all deferred;
This will enable all the constraints violations at the time of commit.
OPERATIONS WITH CONSTRAINTS
Possible operations with constraints as follows.
Enable
Disable
Enforce
Drop
ENABLE
This will enable the constraint. Before enable, the constraint will check the existing data.
Ex:
SQL> alter table student enable constraint un;
DISABLE
This will disable the constraint.
Ex:
SQL> alter table student enable constraint un;
ENFORCE
This will enforce the constraint rather than enable for future inserts or updates.
This will not check for existing data while enforcing data.
Ex:
SQL> alter table student enforce constraint un;
DROP
This will remove the constraint.
Ex:
SQL> alter table student drop constraint un;
Once the table is dropped, constraints automatically will drop.
CASE AND DEFAULT
CASE
Case is similar to decode but easier to understand while going through coding
Ex:
SQL> Select sal,
Case sal
When 500 then ‘low’
When 5000 then ‘high’
Else ‘medium’
End case
From emp;
SAL CASE
----- --------
500 low
2500 medium
2000 medium
3500 medium
3000 medium
5000 high
4000 medium
5000 high
1800 medium
1200 medium
2000 medium
2700 medium
2200 medium
3200 medium
DEFAULT
Default can be considered as a substitute behavior of not null constraint when applied to new rows being entered into the table.
When you define a column with the default keyword followed by a value, you are actually telling the database that, on insert if a row was not assigned a value for this column, use the default value that you have specified.
Default is applied only during insertion of new rows.
Ex:
SQL> create table student(no number(2) default 11,name varchar(2));
SQL> insert into student values(1,'a');
SQL> insert into student(name) values('b');
SQL> select * from student;
NO NAME
------ ---------
1 a
11 b
SQL> insert into student values(null, ‘c’);
SQL> select * from student;
NO NAME
------ ---------
1 a
11 b
C
-- Default can not override nulls.
ABSTRACT DATA TYPES
Some times you may want type which holds all types of data including numbers, chars and special characters something like this. You can not achieve this using pre-defined types.
You can define custom types which holds your desired data.
Ex:
Suppose in a table we have address column which holds hno and city information.
We will define a custom type which holds both numeric as well as char data.
CREATING ADT
SQL> create type addr as object(hno number(3),city varchar(10)); /
CREATING TABLE BASED ON ADT
SQL> create table student(no number(2),name varchar(2),address addr);
INSERTING DATA INTO ADT TABLES
SQL> insert into student values(1,'a',addr(111,'hyd'));
SQL> insert into student values(2,'b',addr(222,'bang'));
SQL> insert into student values(3,'c',addr(333,'delhi'));
SELECTING DATA FROM ADT TABLES
SQL> select * from student;
NO NAME ADDRESS(HNO, CITY)
--- ------- -------------------------
1 a ADDR(111, 'hyd')
2 b ADDR(222, 'bang')
3 c ADDR(333, 'delhi')
SQL> select no,name,s.address.hno,s.address.city from student s;
NO NAME ADDRESS.HNO ADDRESS.CITY
---- ------- ----------------- ----------------
1 a 111 hyd
2 b 222 bang
3 c 333 delhi
UPDATE WITH ADT TABLES
SQL> update student s set s.address.city = 'bombay' where s.address.hno = 333;
SQL> select no,name,s.address.hno,s.address.city from student s;
NO NAME ADDRESS.HNO ADDRESS.CITY
---- ------- ----------------- ----------------
1 a 111 hyd
2 b 222 bang
3 c 333 bombay
DELETE WITH ADT TABLES
SQL> delete student s where s.address.hno = 111;
SQL> select no,name,s.address.hno,s.address.city from student s;
NO NAME ADDRESS.HNO ADDRESS.CITY
---- ------- ----------------- ----------------
2 b 222 bang
3 c 333 bombay
DROPPING ADT
SQL> drop type addr;
OBJECT VIEWS AND METHODS
OBJECT VIEWS
If you want to implement objects with the existing table, object views come into picture.
You define the object and create a view which relates this object to the existing table nothing but object view.
Object views are used to relate the user defined objects to the existing table.
Ex:
1) Assume that the table student has already been created with the following columns
SQL> create table student(no number(2),name varchar(10),hno number(3),city
varchar(10));
2) Create the following types
SQL> create type addr as object(hno number(2),city varchar(10));/
SQL> create type stud as object(name varchar(10),address addr);/
3) Relate the objects to the student table by creating the object view
SQL> create view student_ov(no,stud_info) as select no,stud(name,addr(hno,city)) from
student;
4) Now you can insert data into student table in two ways
a) By regular insert
SQL> Insert into student values(1,’sudha’,111,’hyd’);
b) By using object view
SQL> Insert into student_ov values(1,stud(‘sudha’,addr(111,’hyd’)));
METHODS
You can define methods which are nothing but functions in types and apply in the tables which holds the types;
Ex:
1) Defining methods in types
SQL> Create type stud as object(name varchar(10),marks number(3),
Member function makrs_f(marks in number) return number,
Pragma restrict_references(marks_f,wnds,rnds,wnps,fnps));/
2) Defining type body
SQL> Create type body stud as
Member function marks_f(marks in number) return number is
Begin
Return (marks+100);
End marks_f;
End;/
3) Create a table using stud type
SQL> Create table student(no number(2),info stud);
4) Insert some data into student table
SQL> Insert into student values(1,stud(‘sudha’,100));
5) Using method in select
SQL> Select s.info.marks_f(s.info.marks) from student s;
-- Here we are using the pragma restrict_references to avoid the writes to the database.
VARRAYS AND NESTED TABLES
VARRAYS
A varying array allows you to store repeating attributes of a record in a single row but with limit.
Ex:
1) We can create varrays using oracle types as well as user defined types.
a) Varray using pre-defined types
SQL> Create type va as varray(5) of varchar(10);/
b) Varrays using user defined types
SQL> Create type addr as object(hno number(3),city varchar(10));/
SQL> Create type va as varray(5) of addr;/
2) Using varray in table
SQL> Create table student(no number(2),name varchar(10),address va);
3) Inserting values into varray table
SQL> Insert into student values(1,’sudha’,va(addr(111,’hyd’)));
SQL> Insert into student values(2,’jagan’,va(addr(111,’hyd’),addr(222,’bang’)));
4) Selecting data from varray table
SQL> Select * from student;
-- This will display varray column data along with varray and adt;
SQL> Select no,name, s.* from student s1, table(s1.address) s;
-- This will display in general format
5) Instead of s.* you can specify the columns in varray
SQL> Select no,name, s.hno,s.city from student s1,table(s1.address) s;
-- Update and delete not possible in varrays.
-- Here we used table function which will take the varray column as input for producing
output excluding varray and types.
NESTED TABLES
A nested table is, as its name implies, a table within a table. In this case it is a table that is represented as a column within another table.
Nested table has the same effect of varrays but has no limit.
Ex:
1) We can create nested tables using oracle types and user defined types which has no limit
a) Nested tables using pre-defined types
SQL> Create type nt as table of varchar(10);/
b) Nested tables using user defined types
SQL> Create type addr as object(hno number(3),city varchar(10));/
SQL> Create type nt as table of addr;/
2) Using nested table in table
SQL> Create table student(no number(2),name varchar(10),address nt) nested table
address store as student_temp;
3) Inserting values into table which has nested table
SQL> Insert into student values (1,’sudha’,nt(addr(111,’hyd’)));
SQL> Insert into student values (2,’jagan’,nt(addr(111,’hyd’),addr(222,’bang’)));
4) Selecting data from table which has nested table
SQL> Select * from student;
-- This will display nested table column data along with nested table and adt;
SQL> Select no,name, s.* from student s1, table(s1.address) s;
-- This will display in general format
5) Instead of s.* you can specify the columns in nested table
SQL> Select no,name, s.hno,s.city from student s1,table(s1.address) s;
6) Inserting nested table data to the existing row
SQL> Insert into table(select address from student where no=1)
values(addr(555,’chennai’));
7) Update in nested tables
SQL> Update table(select address from student where no=2) s set s.city=’bombay’ where
s.hno = 222;
8) Delete in nested table
SQL> Delete table(select address from student where no=3) s where s.hno=333;
DATA MODEL
ALL_COLL_TYPES
ALL_TYPES
DBA_COLL_TYPES
DBA_TYPES
USER_COLL_TYPES
USER_TYPES
FLASHBACK QUERY
Used to retrieve the data which has been already committed with out going for recovery.
Flashbacks are of two types
Time base flashback
SCN based flashback (SCN stands for System Change Number)
Ex:
1) Using time based flashback
a) SQL> Select *from student;
-- This will display all the rows
b) SQL> Delete student;
c) SQL> Commit; -- this will commit the work.
d) SQL> Select *from student;
-- Here it will display nothing
e) Then execute the following procedures
SQL> Exec dbms_flashback.enable_at_time(sysdate-2/1440)
f) SQL> Select *from student;
-- Here it will display the lost data
-- The lost data will come but the current system time was used
g) SQL> Exec dbms_flashback.disable
-- Here we have to disable the flashback to enable it again
2) Using SCN based flashback
a) Declare a variable to store SCN
SQL> Variable s number
b) Get the SCN
SQL> Exec :s := exec dbms_flashback.get_system_change_number
c) To see the SCN
SQL> Print s
d) Then execute the following procedures
SQL> Exec dbms_flashback.enable_at_system_change_number(:s)
SQL> Exec dbms_flashback.disable
EXTERNAL TABLES
You can user external table feature to access external files as if they are tables inside the database.
When you create an external table, you define its structure and location with in oracle.
When you query the table, oracle reads the external table and returns the results just as if the data had been stored with in the database.
ACCESSING EXTERNAL TABLE DATA
To access external files from within oracle, you must first use the create directory command to define a directory object pointing to the external file location
Users who will access the external files must have the read and write privilege on the directory.
Ex:
CREATING DIRECTORY AND OS LEVEL FILE
SQL> Sqlplus system/manager
SQL> Create directory saketh_dir as ‘/Visdb/visdb/9.2.0/external’;
SQL> Grant all on directory saketh_dir to saketh;
SQL> Conn saketh/saketh
SQL> Spool dept.lst
SQL> Select deptno || ‘,’ || dname || ‘,’ || loc from dept;
SQL> Spool off
CREATING EXTERNAL TABLE
SQL> Create table dept_ext
(deptno number(2),
Dname varchar(14),
Loc varchar(13))
Organization external ( type oracle_loader
Default directory saketh_dir
Access parameters
( records delimited by newline
Fields terminated by “,”
( deptno number(2),
Dname varchar(14),
Loc varchar(13)))
Location (‘/Visdb/visdb/9.2.0/dept.lst’));
SELECTING DATA FROM EXTERNAL TABLE
SQL> select * from dept_ext;
This will read from dept.lst which is a operating system level file.
LIMITATIONS ON EXTERNAL TABLES
a) You can not perform insert, update, and delete operations
a) Indexing not possible
b) Constraints not possible
BENEFITS OF EXTERNAL TABLES
a) Queries of external tables complete very quickly even though a full table scan id required with each access
b) You can join external tables to each other or to standard tables
REF DEREF VALUE
REF
The ref function allows referencing of existing row objects.
Each of the row objects has an object id value assigned to it.
The object id assigned can be seen by using ref function.
DEREF
The deref function performs opposite action.
It takes a reference value of object id and returns the value of the row objects.
VALUE
Even though the primary table is object table, still it displays the rows in general format.
To display the entire structure of the object, this will be used.
Ex:
1) create vendot_adt type
SQL> Create type vendor_adt as object (vendor_code number(2), vendor_name
varchar(2), vendor_address varchar(10));/
2) create object tables vendors and vendors1
SQL> Create table vendors of vendor_adt;
SQL> Create table vendors1 of vendor_adt;
3) insert the data into object tables
SQL> insert into vendors values(1, ‘a’, ‘hyd’);
SQL> insert into vendors values(2, ‘b’, ‘bang’);
SQL> insert into vendors1 values(3, ‘c’, ‘delhi’);
SQL> insert into vendors1 values(4, ‘d’, ‘chennai’);
4) create another table orders which holds the vendor_adt type also.
SQL> Create table orders (order_no number(2), vendor_info ref vendor_adt);
Or
SQL> Create table orders (order_no number(2), vendor_info ref vendor_adt with rowid);
5) insert the data into orders table
The vendor_info column in the following syntaxes will store object id of any table which
is referenced by vendor_adt object ( both vendors and vendors1).
SQL> insert into orders values(11,(select ref(v) from vendors v where vendor_code = 1));
SQL> insert into orders values(12,(select ref(v) from vendors v where vendor_code = 2));
SQL> insert into orders values(13,(select ref(v1) from vendors1 v1 where vendor_code =
1));
SQL> insert into orders values(14,(select ref(v1) from vendors1 v1 where vendor_code =
1));
6) To see the object ids of vendor table
SQL> Select ref(V) from vendors v;
7) If you see the vendor_info of orders it will show only the object ids not the values, to see
the values
SQL> Select deref(o.vendor_info) from orders o;
8) Even though the vendors table is object table it will not show the adt along with data, to
see the data along with the adt
SQL>Select * from vendors;
This will give the data without adt.
SQL>Select value(v) from vendors v;
This will give the columns data along wih the type.
REF CONSTRAINTS
Ref can also acts as constraint.
Even though vendors1 also holding vendor_adt, the orders table will store the object ids of vendors only because it is constrained to that table only.
The vendor_info column in the following syntaxes will store object ids of vendors only.
SQL> Create table orders (order_no number(2), vendor_info ref vendor_adt scope is
vendors);
Or
SQL> Create table orders (order_no number(2), vendor_info ref vendor_adt constraint fk
references vendors);
OBJECT VIEWS WITH REFERENCES
To implement the objects and the ref constraints to the existing tables, what we can do? Simply drop the both tables and recreate with objects and ref constrains.
But you can achieve this with out dropping the tables and without losing the data by creating object views with references.
Ex:
a) Create the following tables
SQL> Create table student1(no number(2) primary key,name varchar(2),marks
number(3));
SQL> Create table student2(no number(2) primary key,hno number(3),city varchar(10),id
number(2),foreign Key(id) references student1(no));
b) Insert the records into both tables
SQL> insert into student1(1,’a’,100);
SQL> insert into student1(2,’b’,200);
SQL> insert into student2(11,111,’hyd’,1);
SQL> insert into student2(12,222,’bang’,2);
SQL> insert into student2(13,333,’bombay’,1);
c) Create the type
SQL> create or replace type stud as object(no number(2),name varchar(2),marks
number(3));/
d) Generating OIDs
SQL> Create or replace view student1_ov of stud with object identifier(or id) (no) as
Select * from Student1;
e) Generating references
SQL> Create or replace view student2_ov as select no,hno,city,make_ref(student1_ov,id)
id from Student2;
d) Query the following
SQL> select *from student1_ov;
SQL> select ref(s) from student1_ov s;
SQL> select values(s) from student1_ov;
SQ> select *from student2_ov;
SQL> select deref(s.id) from student2_ov s;
PARTITIONS
A single logical table can be split into a number of physically separate pieces based on ranges of key values. Each of the parts of the table is called a partition.
A non-partitioned table can not be partitioned later.
TYPES
Range partitions
List partitions
Hash partitions
Sub partitions
ADVANTAGES
Reducing downtime for scheduled maintenance, which allows maintenance operations to be carried out on selected partitions while other partitions are available to users.
Reducing downtime due to data failure, failure of a particular partition will no way affect other partitions.
Partition independence allows for concurrent use of the various partitions for various purposes.
ADVANTAGES OF PARTITIONS BY STORING THEM IN DIFFERENT TABLESPACES
Reduces the possibility of data corruption in multiple partitions.
Back up and recovery of each partition can be done independently.
DISADVANTAGES
Partitioned tables cannot contain any columns with long or long raw datatypes, LOB types or object types.
RANGE PARTITIONS
a) Creating range partitioned table
SQL> Create table student(no number(2),name varchar(2)) partition by range(no) (partition
p1 values less than(10), partition p2 values less than(20), partition p3 values less
than(30),partition p4 values less than(maxvalue));
** if you are using maxvalue for the last partition, you can not add a partition.
b) Inserting records into range partitioned table
SQL> Insert into student values(1,’a’); -- this will go to p1
SQL> Insert into student values(11,’b’); -- this will go to p2
SQL> Insert into student values(21,’c’); -- this will go to p3
SQL> Insert into student values(31,’d’); -- this will go to p4
c) Retrieving records from range partitioned table
SQL> Select *from student;
SQL> Select *from student partition(p1);
d) Possible operations with range partitions
Add
Drop
Truncate
Rename
Split
Move
Exchange
e) Adding a partition
SQL> Alter table student add partition p5 values less than(40);
f) Dropping a partition
SQL> Alter table student drop partition p4;
g) Renaming a partition
SQL> Alter table student rename partition p3 to p6;
h) Truncate a partition
SQL> Alter table student truncate partition p6;
i) Splitting a partition
SQL> Alter table student split partition p2 at(15) into (partition p21,partition p22);
j) Exchanging a partition
SQL> Alter table student exchange partition p1 with table student2;
k) Moving a partition
SQL> Alter table student move partition p21 tablespace saketh_ts;
LIST PARTITIONS
a) Creating list partitioned table
SQL> Create table student(no number(2),name varchar(2)) partition by list(no) (partition p1
values(1,2,3,4,5), partition p2 values(6,7,8,9,10),partition p3 values(11,12,13,14,15),
partition p4 values(16,17,18,19,20));
b) Inserting records into list partitioned table
SQL> Insert into student values(1,’a’); -- this will go to p1
SQL> Insert into student values(6,’b’); -- this will go to p2
SQL> Insert into student values(11,’c’); -- this will go to p3
SQL> Insert into student values(16,’d’); -- this will go to p4
c) Retrieving records from list partitioned table
SQL> Select *from student;
SQL> Select *from student partition(p1);
d) Possible operations with list partitions
Add
Drop
Truncate
Rename
Move
Exchange
e) Adding a partition
SQL> Alter table student add partition p5 values(21,22,23,24,25);
f) Dropping a partition
SQL> Alter table student drop partition p4;
g) Renaming a partition
SQL> Alter table student rename partition p3 to p6;
h) Truncate a partition
SQL> Alter table student truncate partition p6;
i) Exchanging a partition
SQL> Alter table student exchange partition p1 with table student2;
j) Moving a partition
SQL> Alter table student move partition p2 tablespace saketh_ts;
HASH PARTITIONS
a) Creating hash partitioned table
SQL> Create table student(no number(2),name varchar(2)) partition by hash(no) partitions
5;
Here oracle automatically gives partition names like
SYS_P1
SYS_P2
SYS_P3
SYS_P4
SYS_P5
b) Inserting records into hash partitioned table
it will insert the records based on hash function calculated by taking the partition key
SQL> Insert into student values(1,’a’);
SQL> Insert into student values(6,’b’);
SQL> Insert into student values(11,’c’);
SQL> Insert into student values(16,’d’);
c) Retrieving records from hash partitioned table
SQL> Select *from student;
SQL> Select *from student partition(sys_p1);
d) Possible operations with hash partitions
Add
Truncate
Rename
Move
Exchange
e) Adding a partition
SQL> Alter table student add partition p6 ;
f) Renaming a partition
SQL> Alter table student rename partition p6 to p7;
g) Truncate a partition
SQL> Alter table student truncate partition p7;
h) Exchanging a partition
SQL> Alter table student exchange partition sys_p1 with table student2;
i) Moving a partition
SQL> Alter table student move partition sys_p2 tablespace saketh_ts;
SUB-PARTITIONS WITH RANGE AND HASH
Subpartitions clause is used by hash only. We can not create subpartitions with list and hash partitions.
a) Creating subpartitioned table
SQL> Create table student(no number(2),name varchar(2),marks number(3))
Partition by range(no) subpartition by hash(name) subpartitions 3
(Partition p1 values less than(10),partition p2 values less than(20));
This will create two partitions p1 and p2 with three subpartitions for each partition
P1 – SYS_SUBP1
SYS_SUBP2
SYS_SUBP3
P2 – SYS_SUBP4
SYS_SUBP5
SYS_SUBP6
** if you are using maxvalue for the last partition, you can not add a partition.
b) Inserting records into subpartitioned table
SQL> Insert into student values(1,’a’); -- this will go to p1
SQL> Insert into student values(11,’b’); -- this will go to p2
c) Retrieving records from subpartitioned table
SQL> Select *from student;
SQL> Select *from student partition(p1);
SQL> Select *from student subpartition(sys_subp1);
d) Possible operations with subpartitions
Add
Drop
Truncate
Rename
Split
e) Adding a partition
SQL> Alter table student add partition p3 values less than(30);
f) Dropping a partition
SQL> Alter table student drop partition p3;
g) Renaming a partition
SQL> Alter table student rename partition p2 to p3;
h) Truncate a partition
SQL> Alter table student truncate partition p1;
i) Splitting a partition
SQL> Alter table student split partition p3 at(15) into (partition p31,partition p32);
DATA MODEL
ALL_IND_PARTITIONS
ALL_IND_SUBPARTITIONS
ALL_TAB_PARTITIONS
ALL_TAB_SUBPARTITIONS
DBA_IND_PARTITIONS
DBA_IND_SUBPARTITIONS
DBA_TAB_PARTITIONS
DBA_TAB_SUBPARTITIONS
USER_IND_PARTITIONS
USER_IND_SUBPARTITIONS
USER_TAB_PARTITIONS
USER_TAB_SUBPARTITIONS
GROUP BY AND HAVING
GROUP BY
Using group by, we can create groups of related information.
Columns used in select must be used with group by, otherwise it was not a group by expression.
Ex:
SQL> select deptno, sum(sal) from emp group by deptno;
DEPTNO SUM(SAL)
---------- ----------
10 8750
20 10875
30 9400
SQL> select deptno,job,sum(sal) from emp group by deptno,job;
DEPTNO JOB SUM(SAL)
---------- --------- ----------
10 CLERK 1300
10 MANAGER 2450
10 PRESIDENT 5000
20 ANALYST 6000
20 CLERK 1900
20 MANAGER 2975
30 CLERK 950
30 MANAGER 2850
30 SALESMAN 5600
HAVING
This will work as where clause which can be used only with group by because of absence of where clause in group by.
Ex:
SQL> select deptno,job,sum(sal) tsal from emp group by deptno,job having sum(sal) > 3000;
DEPTNO JOB TSAL
---------- --------- ----------
10 PRESIDENT 5000
20 ANALYST 6000
30 SALESMAN 5600
SQL> select deptno,job,sum(sal) tsal from emp group by deptno,job having sum(sal) > 3000
order by job;
DEPTNO JOB TSAL
---------- --------- ----------
20 ANALYST 6000
10 PRESIDENT 5000
30 SALESMAN 5600
ORDER OF EXECUTION
Group the rows together based on group by clause.
Calculate the group functions for each group.
Choose and eliminate the groups based on the having clause.
Order the groups based on the specified column.
ROLLUP GROUPING CUBE
These are the enhancements to the group by feature.
USING ROLLUP
This will give the salaries in each department in each job category along wih the total salary
fot individual departments and the total salary of all the departments.
SQL> Select deptno,job,sum(sal) from emp group by rollup(deptno,job);
DEPTNO JOB SUM(SAL)
---------- --------- ----------
10 CLERK 1300
10 MANAGER 2450
10 PRESIDENT 5000
10 8750
20 ANALYST 6000
20 CLERK 1900
20 MANAGER 2975
20 10875
30 CLERK 950
30 MANAGER 2850
30 SALESMAN 5600
30 9400
29025
USING GROUPING
In the above query it will give the total salary of the individual departments but with a
blank in the job column and gives the total salary of all the departments with blanks in
deptno and job columns.
To replace these blanks with your desired string grouping will be used
SQL> select decode(grouping(deptno),1,'All Depts',deptno),decode(grouping(job),1,'All
jobs',job),sum(sal) from emp group by rollup(deptno,job);
DECODE(GROUPING(DEPTNO),1,'ALLDEPTS',DEP DECODE(GR SUM(SAL)
----------------------------------- ---------------------------------- --------------
10 CLERK 1300
10 MANAGER 2450
10 PRESIDENT 5000
10 All jobs 8750
20 ANALYST 6000
20 CLERK 1900
20 MANAGER 2975
20 All jobs 10875
30 CLERK 950
30 MANAGER 2850
30 SALESMAN 5600
30 All jobs 9400
All Depts All jobs 29025
Grouping will return 1 if the column which is specified in the grouping function has been
used in rollup.
Grouping will be used in association with decode.
USING CUBE
This will give the salaries in each department in each job category, the total salary for individual departments, the total salary of all the departments and the salaries in each job category.
SQL> select decode(grouping(deptno),1,’All Depts’,deptno),decode(grouping(job),1,’All
Jobs’,job),sum(sal) from emp group by cube(deptno,job);
DECODE(GROUPING(DEPTNO),1,'ALLDEPTS',DEP DECODE(GR SUM(SAL)
----------------------------------- ------------------------------------ ------------
10 CLERK 1300
10 MANAGER 2450
10 PRESIDENT 5000
10 All Jobs 8750
20 ANALYST 6000
20 CLERK 1900
20 MANAGER 2975
20 All Jobs 10875
30 CLERK 950
30 MANAGER 2850
30 SALESMAN 5600
30 All Jobs 9400
All Depts ANALYST 6000
All Depts CLERK 4150
All Depts MANAGER 8275
All Depts PRESIDENT 5000
All Depts SALESMAN 5600
All Depts All Jobs 29025
SET OPERATORS
TYPES
Union
Union all
Intersect
Minus
UNION
This will combine the records of multiple tables having the same structure.
Ex:
SQL> select * from student1 union select * from student2;
UNION ALL
This will combine the records of multiple tables having the same structure but including duplicates.
Ex:
SQL> select * from student1 union all select * from student2;
INTERSECT
This will give the common records of multiple tables having the same structure.
Ex:
SQL> select * from student1 intersect select * from student2;
MINUS
This will give the records of a table whose records are not in other tables having the same structure.
Ex:
SQL> select * from student1 minus select * from student2;
VIEWS
A view is a database object that is a logical representation of a table. It is delivered from a table but has no storage of its own and often may be used in the same manner as a table.
A view takes the output of the query and treats it as a table, therefore a view can be thought of as a stored query or a virtual table.
TYPES
Simple view
Complex view
Simple view can be created from one table where as complex view can be created from multiple tables.
WHY VIEWS?
Provides additional level of security by restricting access to a predetermined set of rows and/or columns of a table.
Hide the data complexity.
Simplify commands for the user.
VIEWS WITHOUT DML
Read only view
View with group by
View with aggregate functions
View with rownum
Partition view
View with distinct
Ex:
SQL> Create view dept_v as select *from dept with read only;
SQL> Create view dept_v as select deptno, sum(sal) t_sal from emp group by deptno;
SQL> Create view stud as select rownum no, name, marks from student;
SQL> Create view student as select *from student1 union select *from student2;
SQL> Create view stud as select distinct no,name from student;
VIEWS WITH DML
View with not null column -- insert with out not null column not possible
-- update not null column to null is not possible
-- delete possible
View with out not null column which was in base table -- insert not possible
-- update, delete possible
View with expression -- insert , update not possible
-- delete possible
View with functions (except aggregate) -- insert, update not possible
-- delete possible
View was created but the underlying table was dropped then we will get the message like “ view has errors ”.
View was created but the base table has been altered but still the view was with the initial definition, we have to replace the view to affect the changes.
Complex view (view with more than one table) -- insert not possible
-- update, delete possible (not always)
CREATING VIEW WITHOUT HAVING THE BASE TABLE
SQL> Create force view stud as select *From student;
-- Once the base table was created then the view is validated.
VIEW WITH CHECK OPTION CONSTRAINT
SQL> Create view stud as select *from student where marks = 500 with check option constraint
Ck;
- Insert possible with marks value as 500
- Update possible excluding marks column
- Delete possible
DROPPING VIEWS
SQL> drop view dept_v;
SYNONYM AND SEQUENCE
SYNONYM
A synonym is a database object, which is used as an alias for a table, view or sequence.
TYPES
Private
Public
Private synonym is available to the particular user who creates.
Public synonym is created by DBA which is available to all the users.
ADVANTAGES
Hide the name and owner of the object.
Provides location transparency for remote objects of a distributed database.
CREATE AND DROP
SQL> create synonym s1 for emp;
SQL> create public synonym s2 for emp;
SQL> drop synonym s1;
SEQUENCE
A sequence is a database object, which can generate unique, sequential integer values.
It can be used to automatically generate primary key or unique key values.
A sequence can be either in an ascending or descending order.
Syntax:
Create sequence
[cycle/nocycle] [cache/nocache];
By defalult the sequence starts with 1, increments by 1 with minvalue of 1 and with nocycle, nocache.
Cache option pre-alloocates a set of sequence numbers and retains them in memory for faster access.
Ex:
SQL> create sequence s;
SQL> create sequence s increment by 10 start with 100 minvalue 5 maxvalue 200 cycle
cache 20;
USING SEQUENCE
SQL> create table student(no number(2),name varchar(10));
SQL> insert into student values(s.nextval, ‘saketh’);
Initially currval is not defined and nextval is starting value.
After that nextval and currval are always equal.
CREATING ALPHA-NUMERIC SEQUENCE
SQL> create sequence s start with 111234;
SQL> Insert into student values (s.nextval || translate
(s.nextval,’1234567890’,’abcdefghij’));
ALTERING SEQUENCE
We can alter the sequence to perform the following.
Set or eliminate minvalue or maxvalue.
Change the increment value.
Change the number of cached sequence numbers.
Ex:
SQL> alter sequence s minvalue 5;
SQL> alter sequence s increment by 2;
SQL> alter sequence s cache 10;
DROPPING SEQUENCE
SQL> drop sequence s;
JOINS
The purpose of a join is to combine the data across tables.
A join is actually performed by the where clause which combines the specified rows of tables.
If a join involves in more than two tables then oracle joins first two tables based on the joins condition and then compares the result with the next table and so on.
TYPES
Equi join
Non-equi join
Self join
Natural join
Cross join
Outer join
Left outer
Right outer
Full outer
Inner join
Using clause
On clause
Assume that we have the following tables.
SQL> select * from dept;
DEPTNO DNAME LOC
------ ---------- ----------
10 mkt hyd
20 fin bang
30 hr bombay
SQL> select * from emp;
EMPNO ENAME JOB MGR DEPTNO
---------- ---------- ---------- ---------- ----------
111 saketh analyst 444 10
222 sudha clerk 333 20
333 jagan manager 111 10
444 madhu engineer 222 40
EQUI JOIN
A join which contains an ‘=’ operator in the joins condition.
Ex:
SQL> select empno,ename,job,dname,loc from emp e,dept d where e.deptno=d.deptno;
EMPNO ENAME JOB DNAME LOC
---------- ---------- ---------- ---------- ----------
111 saketh analyst mkt hyd
333 jagan manager mkt hyd
222 sudha clerk fin bang
USING CLAUSE
SQL> select empno,ename,job ,dname,loc from emp e join dept d using(deptno);
EMPNO ENAME JOB DNAME LOC
---------- ---------- ---------- ---------- ----------
111 saketh analyst mkt hyd
333 jagan manager mkt hyd
222 sudha clerk fin bang
ON CLAUSE
SQL> select empno,ename,job,dname,loc from emp e join dept d on(e.deptno=d.deptno);
EMPNO ENAME JOB DNAME LOC
---------- ---------- ---------- ---------- ----------
111 saketh analyst mkt hyd
333 jagan manager mkt hyd
222 sudha clerk fin bang
NON-EQUI JOIN
A join which contains an operator other than ‘=’ in the joins condition.
Ex:
SQL> select empno,ename,job,dname,loc from emp e,dept d where e.deptno > d.deptno;
EMPNO ENAME JOB DNAME LOC
---------- ---------- ---------- ---------- ----------
222 sudha clerk mkt hyd
444 madhu engineer mkt hyd
444 madhu engineer fin bang
444 madhu engineer hr bombay
SELF JOIN
Joining the table itself is called self join.
Ex:
SQL> select e1.empno,e2.ename,e1.job,e2.deptno from emp e1,emp e2 where
e1.empno=e2.mgr;
EMPNO ENAME JOB DEPTNO
---------- ---------- ---------- ----------
111 jagan analyst 10
222 madhu clerk 40
333 sudha manager 20
444 saketh engineer 10
NATURAL JOIN
Natural join compares all the common columns.
Ex:
SQL> select empno,ename,job,dname,loc from emp natural join dept;
EMPNO ENAME JOB DNAME LOC
---------- ---------- ---------- ---------- ----------
111 saketh analyst mkt hyd
333 jagan manager mkt hyd
222 sudha clerk fin bang
CROSS JOIN
This will gives the cross product.
Ex:
SQL> select empno,ename,job,dname,loc from emp cross join dept;
EMPNO ENAME JOB DNAME LOC
---------- ---------- ---------- ---------- ----------
111 saketh analyst mkt hyd
222 sudha clerk mkt hyd
333 jagan manager mkt hyd
444 madhu engineer mkt hyd
111 saketh analyst fin bang
222 sudha clerk fin bang
333 jagan manager fin bang
444 madhu engineer fin bang
111 saketh analyst hr bombay
222 sudha clerk hr bombay
333 jagan manager hr bombay
444 madhu engineer hr bombay
OUTER JOIN
Outer join gives the non-matching records along with matching records.
LEFT OUTER JOIN
This will display the all matching records and the records which are in left hand side table those that are not in right hand side table.
Ex:
SQL> select empno,ename,job,dname,loc from emp e left outer join dept d
on(e.deptno=d.deptno);
Or
SQL> select empno,ename,job,dname,loc from emp e,dept d where e.deptno=d.deptno(+);
EMPNO ENAME JOB DNAME LOC
---------- ---------- ---------- ---------- ----------
111 saketh analyst mkt hyd
333 jagan manager mkt hyd
222 sudha clerk fin bang
444 madhu engineer
RIGHT OUTER JOIN
This will display the all matching records and the records which are in right hand side table those that are not in left hand side table.
Ex:
SQL> select empno,ename,job,dname,loc from emp e right outer join dept d
on(e.deptno=d.deptno);
Or
SQL> select empno,ename,job,dname,loc from emp e,dept d where e.deptno(+) = d.deptno;
EMPNO ENAME JOB DNAME LOC
---------- ---------- ---------- ---------- ----------
111 saketh analyst mkt hyd
333 jagan manager mkt hyd
222 sudha clerk fin bang
hr bombay
FULL OUTER JOIN
This will display the all matching records and the non-matching records from both tables.
Ex:
SQL> select empno,ename,job,dname,loc from emp e full outer join dept d
on(e.deptno=d.deptno);
EMPNO ENAME JOB DNAME LOC
---------- ---------- ---------- ---------- ----------
333 jagan manager mkt hyd
111 saketh analyst mkt hyd
222 sudha clerk fin bang
444 madhu engineer
hr bombay
INNER JOIN
This will display all the records that have matched.
Ex:
SQL> select empno,ename,job,dname,loc from emp inner join dept using(deptno);
EMPNO ENAME JOB DNAME LOC
---------- ---------- ---------- ---------- ----------
111 saketh analyst mkt hyd
333 jagan manager mkt hyd
222 sudha clerk fin bang
SUBQUERIES AND EXISTS
SUBQUERIES
Nesting of queries, one within the other is termed as a subquery.
A statement containing a subquery is called a parent query.
Subqueries are used to retrieve data from tables that depend on the values in the table itself.
TYPES
Single row subqueries
Multi row subqueries
Multiple subqueries
Correlated subqueries
SINGLE ROW SUBQUERIES
In single row subquery, it will return one value.
Ex:
SQL> select * from emp where sal > (select sal from emp where empno = 7566);
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- ------------ ------- ---------- ----------
7788 SCOTT ANALYST 7566 19-APR-87 3000 20
7839 KING PRESIDENT 17-NOV-81 5000 10
7902 FORD ANALYST 7566 03-DEC-81 3000 20
MULTI ROW SUBQUERIES
In multi row subquery, it will return more than one value. In such cases we should include operators like any, all, in or not in between the comparision operator and the subquery.
Ex:
SQL> select * from emp where sal > any (select sal from emp where sal between 2500 and
4000);
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- ----------- -------- ---------- ----------
7566 JONES MANAGER 7839 02-APR-81 2975 20
7788 SCOTT ANALYST 7566 19-APR-87 3000 20
7839 KING PRESIDENT 17-NOV-81 5000 10
7902 FORD ANALYST 7566 03-DEC-81 3000 20
SQL> select * from emp where sal > all (select sal from emp where sal between 2500 and
4000);
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- ------------- ------ ---------- ----------
7839 KING PRESIDENT 17-NOV-81 5000 10
MULTIPLE SUBQUERIES
There is no limit on the number of subqueries included in a where clause. It allows nesting of a query within a subquery.
Ex:
SQL> select * from emp where sal = (select max(sal) from emp where sal < (select
max(sal) from emp));
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ---------- ------------ ------- ---------- ----------
7788 SCOTT ANALYST 7566 19-APR-87 3000 20
7902 FORD ANALYST 7566 03-DEC-81 3000 20
CORRELATED SUBQUERIES
A subquery is evaluated once for the entire parent statement where as a correlated subquery is evaluated once for every row processed by the parent statement.
Ex:
SQL> select distinct deptno from emp e where 5 <= (select count(ename) from emp where
e.deptno = deptno);
DEPTNO
----------
20
30
EXISTS
Exists function is a test for existence. This is a logical test for the return of rows from a query.
Ex:
Suppose we want to display the department numbers which has more than 4 employees.
SQL> select deptno,count(*) from emp group by deptno having count(*) > 4;
DEPTNO COUNT(*)
--------- ----------
20 5
30 6
From the above query can you want to display the names of employees?
SQL> select deptno,ename, count(*) from emp group by deptno,ename having count(*) > 4;
no rows selected
The above query returns nothing because combination of deptno and ename never return
more than one count.
The solution is to use exists which follows.
SQL> select deptno,ename from emp e1 where exists (select * from emp e2
where e1.deptno=e2.deptno group by e2.deptno having count(e2.ename) > 4) order by
deptno,ename;
DEPTNO ENAME
---------- ----------
20 ADAMS
20 FORD
20 JONES
20 SCOTT
20 SMITH
30 ALLEN
30 BLAKE
30 JAMES
30 MARTIN
30 TURNER
30 WARD
NOT EXISTS
SQL> select deptno,ename from emp e1 where not exists (select * from emp e2
where e1.deptno=e2.deptno group by e2.deptno having count(e2.ename) > 4) order by
deptno,ename;
DEPTNO ENAME
--------- ----------
10 CLARK
10 KING
10 MILLER
WALKUP TREES AND INLINE VIEW
WALKUP TREES
Using hierarchical queries, you can retrieve data based on a natural hierarchical relationship between rows in a table. However, where a hierarchical relationship exists between the rows of a table, a process called tree walking enables the hierarchy to be constructed.
Ex:
SQL> select ename || '==>' || prior ename, level from emp start with ename = 'KING'
connect by prior empno=mgr;
ENAME||'==>'||PRIORENAM LEVEL
------------------------------------ --------
KING==> 1
JONES==>KING 2
SCOTT==>JONES 3
ADAMS==>SCOTT 4
FORD==>JONES 3
SMITH==>FORD 4
BLAKE==>KING 2
ALLEN==>BLAKE 3
WARD==>BLAKE 3
MARTIN==>BLAKE 3
TURNER==>BLAKE 3
JAMES==>BLAKE 3
CLARK==>KING 2
MILLER==>CLARK 3
In the above
Start with clause specifies the root row of the table.
Level pseudo column gives the 1 for root , 2 for child and so on.
Connect by prior clause specifies the columns which has parent-child relationship.
INLINE VIEW OR TOP-N ANALYSIS
In the select statement instead of table name, replacing the select statement is known as inline view.
Ex:
SQL> Select ename, sal, rownum rank from (select *from emp order by sal);
ENAME SAL RANK
---------- ---------- ----------
SMITH 800 1
JAMES 950 2
ADAMS 1100 3
WARD 1250 4
MARTIN 1250 5
MILLER 1300 6
TURNER 1500 7
ALLEN 1600 8
CLARK 2450 9
BLAKE 2850 10
JONES 2975 11
SCOTT 3000 12
FORD 3000 13
KING 5000 14
LOCKS
Locks are the mechanisms used to prevent destructive interaction between users accessing same resource simultaneously. Locks provides high degree of data concurrency.
TYPES
Row level locks
Table level locks
ROW LEVEL LOCKS
In the row level lock a row is locked exclusively so that other cannot modify the row until the transaction holding the lock is committed or rolled back. This can be done by using select..for update clause.
Ex:
SQL> select * from emp where sal > 3000 for update of comm.;
TABLE LEVEL LOCKS
A table level lock will protect table data thereby guaranteeing data integrity when data is being accessed concurrently by multiple users. A table lock can be held in several modes.
Share lock
Share update lock
Exclusive lock
SHARE LOCK
A share lock locks the table allowing other users to only query but not insert, update or delete rows in a table. Multiple users can place share locks on the same resource at the same time.
Ex:
SQL> lock table emp in share mode;
SHARE UPDATE LOCK
It locks rows that are to be updated in a table. It permits other users to concurrently query, insert , update or even lock other rows in the same table. It prevents the other users from updating the row that has been locked.
Ex:
SQL> lock table emp in share update mode;
EXCLUSIVE LOCK
Exclusive lock is the most restrictive of tables locks. When issued by any user, it allows the other user to only query. It is similar to share lock but only one user can place exclusive lock on a table at a time.
Ex:
SQL> lock table emp in share exclusive mode;
NOWAIT
If one user locked the table without nowait then another user trying to lock the same table then he has to wait until the user who has initially locked the table issues a commit or rollback statement. This delay could be avoided by appending a nowait clause in the lock table command.
Ex:
SQL> lock table emp in exclusive mode nowait.
DEADLOCK
A deadlock occurs when tow users have a lock each on separate object, and they want to acquire a lock on the each other’s object. When this happens, the first user has to wait for the second user to release the lock, but the second user will not release it until the lock on the first user’s object is freed. In such a case, oracle detects the deadlock automatically and solves the problem by aborting one of the two transactions.
INDEXES
Index is typically a listing of keywords accompanied by the location of information on a subject. We can create indexes explicitly to speed up SQL statement execution on a table. The index points directly to the location of the rows containing the value.
WHY INDEXES?
Indexes are most useful on larger tables, on columns that are likely to appear in where clauses as simple equality.
TYPES
Unique index
Non-unique index
Btree index
Bitmap index
Composite index
Reverse key index
Function-based index
Descending index
Domain index
Object index
Cluster index
Text index
Index organized table
Partition index
Local index
Local prefixed
Local non-prefixed
Global index
Global prefixed
Global non-prefixed
UNIQUE INDEX
Unique indexes guarantee that no two rows of a table have duplicate values in the columns that define the index. Unique index is automatically created when primary key or unique constraint is created.
Ex:
SQL> create unique index stud_ind on student(sno);
NON-UNIQUE INDEX
Non-Unique indexes do not impose the above restriction on the column values.
Ex:
SQL> create index stud_ind on student(sno);
BTREE INDEX or ASCENDING INDEX
The default type of index used in an oracle database is the btree index. A btree index is designed to provide both rapid access to individual rows and quick access to groups of rows within a range. The btree index does this by performing a succession of value comparisons. Each comparison eliminates many of the rows.
Ex:
SQL> create index stud_ind on student(sno);
BITMAP INDEX
This can be used for low cardinality columns: that is columns in which the number of distinct values is snall when compared to the number of the rows in the table.
Ex:
SQL> create bitmap index stud_ind on student(sex);
COMPOSITE INDEX
A composite index also called a concatenated index is an index created on multiple columns of a table. Columns in a composite index can appear in any order and need not be adjacent columns of the table.
Ex:
SQL> create bitmap index stud_ind on student(sno, sname);
REVERSE KEY INDEX
A reverse key index when compared to standard index, reverses each byte of the column being indexed while keeping the column order. When the column is indexed in reverse mode then the column values will be stored in an index in different blocks as the starting value differs. Such an arrangement can help avoid performance degradations in indexes where modifications to the index are concentrated on a small set of blocks.
Ex:
SQL> create index stud_ind on student(sno, reverse);
We can rebuild a reverse key index into normal index using the noreverse keyword.
Ex:
SQL> alter index stud_ind rebuild noreverse;
FUNCTION BASED INDEX
This will use result of the function as key instead of using column as the value for the key.
Ex:
SQL> create index stud_ind on student(upper(sname));
DESCENDING INDEX
The order used by B-tree indexes has been ascending order. You can categorize data in B-tree index in descending order as well. This feature can be useful in applications where sorting operations are required.
Ex:
SQL> create index stud_ind on student(sno desc);
TEXT INDEX
Querying text is different from querying data because words have shades of meaning, relationships to other words, and opposites. You may want to search for words that are near each other, or words that are related to thers. These queries would be extremely difficult if all you had available was the standard relational operators. By extending SQL to include text indexes, oracle text permits you to ask very complex questions about the text.
To use oracle text, you need to create a text index on the column in which the text is stored. Text index is a collection of tables and indexes that store information about the text stored in the column.
TYPES
There are several different types of indexes available in oracle 9i. The first, CONTEXT is supported in oracle 8i as well as oracle 9i. As of oracle 9i, you can use the CTXCAT text index fo further enhance your text index management and query capabilities.
CONTEXT
CTXCAT
CTXRULE
The CTXCAT index type supports the transactional synchronization of data between the base table and its text index. With CONTEXT indexes, you need to manually tell oracle to update the values in the text index after data changes in base table. CTXCAT index types do not generate score values during the text queries.
HOW TO CREATE TEXT INDEX?
You can create a text index via a special version of the create index comman. For context index, specify the ctxsys.context index type and for ctxcat index, specify the ctxsys.ctxcat index type.
Ex:
Suppose you have a table called BOOKS with the following columns
Title, Author, Info.
SQL> create index book_index on books(info) indextype is ctxsys.context;
SQL> create index book_index on books(info) indextype is ctxsys.ctxcat;
TEXT QUERIES
Once a text index is created on the info column of BOOKS table, text-searching capabilities increase dynamically.
CONTAINS & CATSEARCH
CONTAINS function takes two parameters – the column name and the search string.
Syntax:
Contains(indexed_column, search_str);
If you create a CTXCAT index, use the CATSEARCH function in place of CONTAINS. CATSEARCH takes three parameters – the column name, the search string and the index set.
Syntax:
Contains(indexed_column, search_str, index_set);
HOW A TEXT QEURY WORKS?
When a function such as CONTAINS or CATSEARCH is used in query, the text portion of the query is processed by oracle text. The remainder of the query is processed just like a regular query within the database. The result of the text query processing and the regular query processing are merged to return a single set of records to the user.
SEARCHING FOR AN EXACT MATCH OF A WORD
The following queries will search for a word called ‘prperty’ whose score is greater than zero.
SQL> select * from books where contains(info, ‘property’) > 0;
SQL> select * from books where catsearch(info, ‘property’, null) > 0;
Suppose if you want to know the score of the ‘property’ in each book, if score values for individual searches range from 0 to 10 for each occurrence of the string within the text then use the score function.
SQL> select title, score(10) from books where contains(info, ‘property’, 10) > 0;
SEARCHING FOR AN EXACT MATCH OF MULTIPLE WORDS
The following queries will search for two words.
SQL> select * from books where contains(info, ‘property AND harvests’) > 0;
SQL> select * from books where catsearch(info, ‘property AND harvests’, null) > 0;
Instead of using AND you could hae used an ampersand(&). Before using this method, set define off so the & character will not be seen as part of a variable name.
SQL> set define off
SQL> select * from books where contains(info, ‘property & harvests’) > 0;
SQL> select * from books where catsearch(info, ‘property harvests’, null) > 0;
The following queries will search for more than two words.
SQL> select * from books where contains(info, ‘property AND harvests AND workers’) > 0;
SQL> select * from books where catsearch(info, ‘property harvests workers’, null) > 0;
The following queries will search for either of the two words.
SQL> select * from books where contains(info, ‘property OR harvests’) > 0;
Instead of OR you can use a vertical line (|).
SQL> select * from books where contains(info, ‘property | harvests’) > 0;
SQL> select * from books where catsearch(info, ‘property | harvests’, null) > 0;
In the following queries the ACCUM(accumulate) operator adds together the scores of the individual searches and compares the accumulated score to the threshold value.
SQL> select * from books where contains(info, ‘property ACCUM harvests’) > 0;
SQL> select * from books where catsearch(info, ‘property ACCUM harvests’, null) > 0;
Instead of OR you can use a comma(,).
SQL> select * from books where contains(info, ‘property , harvests’) > 0;
SQL> select * from books where catsearch(info, ‘property , harvests’, null) > 0;
In the following queries the MINUS operator subtracts the score of the second term’s search from the score of the first term’s search.
SQL> select * from books where contains(info, ‘property MINUS harvests’) > 0;
SQL> select * from books where catsearch(info, ‘property NOT harvests’, null) > 0;
Instead of MINUS you can use – and instead of NOT you can use ~.
SQL> select * from books where contains(info, ‘property - harvests’) > 0;
SQL> select * from books where catsearch(info, ‘property ~ harvests’, null) > 0;
SEARCHING FOR AN EXACT MATCH OF A PHRASE
The following queries will search for the phrase. If the search phrase includes a reserved word within oracle text, the you must use curly braces ({}) to enclose text.
SQL> select * from books where contains(info, ‘transactions {and} finances’) > 0;
SQL> select * from books where catsearch(info, ‘transactions {and} finances’, null) > 0;
You can enclose the entire phrase within curly braces, in which case any reserved words within the phrase will be treated as part of the search criteria.
SQL> select * from books where contains(info, ‘{transactions and finances}’) > 0;
SQL> select * from books where catsearch(info, ‘{transactions and finances}’, null) > 0;
SEARCHING FOR WORDS THAT ARE NEAR EACH OTHER
The following queries will search for the words that are in between the search terms.
SQL> select * from books where contains(info, ‘workers NEAR harvests’) > 0;
Instead of NEAR you can use ;.
SQL> select * from books where contains(info, ‘workers ; harvests’) > 0;
In CONTEXT index queries, you can specify the maximum number of words between the search terms.
SQL> select * from books where contains(info, ‘NEAR((workers, harvests),10)’ > 0;
USING WILDCARDS DURING SEARCHES
You can use wildcards to expand the list of valid search terms used during your query. Just as in regular text-string wildcard processing, two wildcards are available.
% - percent sign; multiple-character wildcard
_ - underscore; single-character wildcard
SQL> select * from books where contains(info, ‘worker%’) > 0;
SQL> select * from books where contains(info, ‘work___’) > 0;
SEARCHING FOR WORDS THAT SHARE THE SAME STEM
Rather than using wildcards, you can use stem-expansion capabilities to expand the list of text strings. Given the ‘stem’ of a word, oracle will expand the list of words to search for to include all words having the same stem. Sample expansions are show here.
Play - plays playing played playful
SQL> select * from books where contains(info, ‘$manage’) > 0;
SEARCHING FOR FUZZY MATCHES
A fuzzy match expands the specified search term to include words that are spelled similarly but that do not necessarily have the same word stem. Fuzzy matches are most helpful when the text contains misspellings. The misspellings can be either in the searched text or in the search string specified by the user during the query.
The following queries will not return anything because its search does not contain the word ‘hardest’.
SQL> select * from books where contains(info, ‘hardest’) > 0;
It does, however, contains the word ‘harvest’. A fuzzy match will return the books containing the word ‘harvest’ even though ‘harvest’ has a different word stem thant the word used as the search term.
To use a fuzzy match, precede the search term with a question mark, with no space between the question mark and the beginning of the search term.
SQL> select * from books where contains(info, ‘?hardest’) > 0;
SEARCHING FOR WORDS THAT SOUND LIKE OTHER WORDS
SOUNDEX, expands search terms based on how the word sounds. The SOUNDEX expansion method uses the same text-matching logic available via the SOUNDEX function in SQL.
To use the SOUNDEX option, you must precede the search term with an exclamation mark(!).
SQL> select * from books where contains(info, ‘!grate’) > 0;
INDEX SYNCHRONIZATION
When using CONTEXT indexes, you need to manage the text index contents; the text indexes are not updated when the base table is updated. When the table was updated, its text index is out of sync with the base table. To sync of the index, execute the SYNC_INDEX procedure of the CTX_DDL package.
SQL> exec CTX_DDL.SYNC_INDEX(‘book_index’);
INDEX SETS
Historically, problems with queries of text indexes have occurred when other criteria are used alongside text searches as part of the where clause. To improve the mixed query capability, oracle features index sets. The indexes within the index set may be structured relational columns or on text columns.
To create an index set, use the CTX_DDL package to create the index set and add indexes to it. When you create a text index, you can then specify the index set it belongs to.
SQL> exec CTX_DDL.CREATE_INDEX_SET(‘books_index_set’);
The add non-text indexes.
SQL> exec CTX_DDL.ADD_INDEX(‘books_index_set’, ‘title_index’);
Now create a CTXCAT text index. Specify ctxsys.ctxcat as the index type, and list the index set in the parameters clause.
SQL> create index book_index on books(info) indextype is ctxsys.ctxcat parameters(‘index set books_index_set’);
INDEX-ORGANIZED TABLE
An index-organized table keeps its data sorted according to the primary key column values for the table. Index-organized tables store their data as if the entire table was stored in an index.
An index-organized table allows you to store the entire table’s data in an index.
Ex:
SQL> create table student (sno number(2),sname varchar(10),smarks number(3) constraint
pk primary key(sno) organization index;
PARTITION INDEX
Similar to partitioning tables, oracle allows you to partition indexes too. Like table partitions, index partitions could be in different tablespaces.
LOCAL INDEXES
Local keyword tells oracle to create a separte index for each partition.
In the local prefixed index the partition key is specified on the left prefix. When the underlying table is partitioned baes on, say two columns then the index can be prefixed on the first column specified.
Local prefixed indexes can be unique or non unique.
Local indexes may be easier to manage than global indexes.
Ex:
SQL> create index stud_index on student(sno) local;
GLOBAL INDEXES
A global index may contain values from multiple partitions.
An index is global prefixed if it is partitioned on the left prefix of the index columns.
The global clause allows you to create a non-partitioned index.
Global indexes may perform uniqueness checks faster than local (partitioned) indexes.
You cannot create global indexes for hash partitions or subpartitions.
Ex:
SQL> create index stud_index on student(sno) global;
Similar to table partitions, it is possible to move them from one device to another. But unlike table partitions, movement of index partitions requires individual reconstruction of the index or each partition (only in the case of global index).
Ex:
SQL> alter index stud_ind rebuild partition p2
Index partitions cannot be dropped manually.
They are dropped implicitly when the data they refer to is dropped from the partitioned table.
MONITORING USE OF INDEXES
Once you turned on the monitoring the use of indexes, then we can check whether the table is hitting the index or not.
To monitor the use of index use the follwing syntax.
Syntax:
alter index index_name monitoring usage;
then check for the details in V$OBJECT_USAGE view.
If you want to stop monitoring use the following.
Syntax:
alter index index_name nomonitoring usage;
DATA MODEL
ALL_INDEXES
DBA_INDEXES
USER_INDEXES
ALL_IND-COLUMNS
DBA-IND_COLUMNS
USER_IND_COLUMNS
ALL_PART_INDEXES
DBA_PART_INDEXES
USER_PART_INDEXES
V$OBJECT_USAGE
SQL*PLUS COMMNANDS
These commands does not require statement terminator and applicable to the sessions , those will be automatically cleared when session was closed.
BREAK
This will be used to breakup the data depending on the grouping.
Syntax:
Break or bre [on
COMPUTE
This will be used to perform group functions on the data.
Syntax:
Compute or comp [group_function of column_name on breaking_column_name or
report]
TTITLE
This will give the top title for your report. You can on or off the ttitle.
Syntax:
Ttitle or ttit [left | center | right] title_name skip n other_characters
Ttitle or ttit [on or off]
BTITLE
This will give the bottom title for your report. You can on or off the btitle.
Syntax:
Btitle or btit [left | center | right] title_name skip n other_characters
Btitle or btit [on or off]
Ex:
SQL> bre on deptno skip 1 on report
SQL> comp sum of sal on deptno
SQL> comp sum of sal on report
SQL> ttitle center 'EMPLOYEE DETAILS' skip1 center '----------------'
SQL> btitle center '** THANKQ **'
SQL> select * from emp order by deptno;
Output:
EMPLOYEE DETAILS
-----------------------
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
---------- ---------- --------- ------- -------------- -------- ---------- ----------
7782 CLARK MANAGER 7839 09-JUN-81 2450 10
7839 KING PRESIDENT 17-NOV-81 5000
7934 MILLER CLERK 7782 23-JAN-82 1300
---------- **********
8750 sum
7369 SMITH CLERK 7902 17-DEC-80 800 20
7876 ADAMS CLERK 7788 23-MAY-87 1100
7902 FORD ANALYST 7566 03-DEC-81 3000
7788 SCOTT ANALYST 7566 19-APR-87 3000
7566 JONES MANAGER 7839 02-APR-81 2975
---------- **********
10875 sum
7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30
7698 BLAKE MANAGER 7839 01-MAY-81 2850
7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400
7900 JAMES CLERK 7698 03-DEC-81 950
7844 TURNER SALESMAN 7698 08-SEP-81 1500 0
7521 WARD SALESMAN 7698 22-FEB-81 1250 500
---------- **********
9400 sum
----------
sum 29025
** THANKQ **
CLEAR
This will clear the existing buffers or break or computations or columns formatting.
Syntax:
Clear or cle buffer | bre | comp | col;
Ex:
SQL> clear buffer
Buffer cleared
SQL> clear bre
Breaks cleared
SQL> clear comp
Computes cleared
SQL> clear col
Columns cleared
CHANGE
This will be used to replace any strings in SQL statements.
Syntax:
Change or c/old_string/new_string
If the old_string repeats many times then new_string replaces the first string only.
Ex:
SQL> select * from det;
select * from det
*
ERROR at line 1:
ORA-00942: table or view does not exist
SQL> c/det/dept
1* select * from dept
SQL> /
DEPTNO DNAME LOC
---------- ---------------- -----------
10 ACCOUNTING NEW YORK
20 RESEARCH ALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON
COLUMN
This will be used to increase or decrease the width of the table columns.
Syntax:
Column or col
Ex:
SQL> col deptno format 999
SQL> col dname format a10
SAVE
This will be used to save your current SQL statement as SQL Script file.
Syntax:
Save or sav
If you want to save the filename with existing filename the you have to use replace option.
By default it will take sql as the extension.
Ex:
SQL> save ss
Created file ss.sql
SQL> save ss replace
Wrote file ss.sql
EXECUTE
This will be used to execute stored subprograms or packaged subprograms.
Syntax:
Execute or exec
Ex:
SQL> exec sample_proc
SPOOL
This will record the data when you spool on, upto when you say spool off. By default it will give lst as extension.
Syntax:
Spool on | off | out |
Ex:
SQL> spool on
SQL> select * from dept;
DEPTNO DNAME LOC
--------- -------------- ----------
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON
SQL> spool off
SQL> ed on.lst
SQL> select * from dept;
DEPTNO DNAME LOC
--------- -------------- ----------
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON
SQL> spool off
LIST
This will give the current SQL statement.
Syntax:
List or li [start_line_number] [end_line_number]
Ex:
SQL> select
2 *
3 from
4 dept;
SQL> list
1 select
2 *
3 from
4* dept
SQL> list 1
1* select
SQL> list 3
3* from
SQL> list 1 3
1 select
2 *
3* from
INPUT
This will insert the new line to the current SQL statement.
Syntax:
Input or in
Ex:
SQL> select *
SQL> list
1* select *
SQL> input from dept
SQL> list
1 select *
2* from dept
APPEND
This will adds a new string to the existing string in the SQL statement without any space.
Syntax:
Append or app
Ex:
SQL> select *
SQL> list
1* select *
SQL> append from dept
1* select * from dept
SQL> list
1* select * from dept
DELETE
This will delete the current SQL statement lines.
Syntax:
Delete or del
Ex:
SQL> select
2 *
3 from
4 dept
5 where
6 deptno
7 >10;
SQL> list
1 select
2 *
3 from
4 dept
5 where
6 deptno
7* >10
SQL> del 1
SQL> list
1 *
2 from
3 dept
4 where
5 deptno
6* >10
SQL> del 2
SQL> list
1 *
2 dept
3 where
4 deptno
5* >10
SQL> del 2 4
SQL> list
1 *
2* >10
SQL> del
SQL> list
1 *
VARIABLE
This will be used to declare a variable.
Syntax:
Variable or var
Ex:
SQL> var dept_name varchar(15)
SQL> select dname into dept_name from dept where deptno = 10;
This will be used to print the output of the variables that will be declared at SQL level.
Syntax:
Ex:
SQL> print dept_name
DEPT_NAME
--------------
ACCOUNTING
START
This will be used to execute SQL scripts.
Syntax:
start
Ex:
SQL> start ss.sql
SQL> @ss.sql -- this will execute sql script files only.
HOST
This will be used to interact with the OS level from SQL.
Syntax:
Host [operation]
Ex:
SQL> host
SQL> host dir
SHOW
Using this, you can see several commands that use the set command and status.
Syntax:
Show all |
Ex:
SQL> show all
appinfo is OFF and set to "SQL*Plus"
arraysize 15
autocommit OFF
autoprint OFF
autorecovery OFF
autotrace OFF
blockterminator "." (hex 2e)
btitle OFF and is the first few characters of the next SELECT statement
cmdsep OFF
colsep " "
compatibility version NATIVE
concat "." (hex 2e)
copycommit 0
COPYTYPECHECK is ON
define "&" (hex 26)
describe DEPTH 1 LINENUM OFF INDENT ON
echo OFF
editfile "afiedt.buf"
embedded OFF
escape OFF
FEEDBACK ON for 6 or more rows
flagger OFF
flush ON
SQL> sho verify
verify OFF
RUN
This will runs the command in the buffer.
Syntax:
Run | /
Ex:
SQL> run
SQL> /
STORE
This will save all the set command statuses in a file.
Syntax:
Store set
Ex:
SQL> store set my_settings.scmd
Created file my_settings.scmd
SQL> store set my_settings.cmd replace
Wrote file my_settings.cmd
SQL> store set my_settings.cmd append
Appended file to my_settings.cmd
FOLD_AFTER
This will fold the columns one after the other.
Syntax:
Column
Ex:
SQL> col deptno fold_after 1
SQL> col dname fold_after 1
SQL> col loc fold_after 1
SQL> set heading off
SQL> select * from dept;
10
ACCOUNTING
NEW YORK
20
RESEARCH
DALLAS
30
SALES
CHICAGO
40
OPERATIONS
BOSTON
FOLD_BEFORE
This will fold the columns one before the other.
Syntax:
Column
DEFINE
This will give the list of all the variables currently defined.
Syntax:
Define [variable_name]
Ex:
SQL> define
DEFINE _DATE = "16-MAY-07" (CHAR)
DEFINE _CONNECT_IDENTIFIER = "oracle" (CHAR)
DEFINE _USER = "SCOTT" (CHAR)
DEFINE _PRIVILEGE = "" (CHAR)
DEFINE _SQLPLUS_RELEASE = "1001000200" (CHAR)
DEFINE _EDITOR = "Notepad" (CHAR)
DEFINE _O_VERSION = "Oracle Database 10g Enterprise Edition Release 10.1.0.2.0 –
Production With the Partitioning, OLAP and Data Mining
options" (CHAR)
DEFINE _O_RELEASE = "1001000200" (CHAR)
SET COMMANDS
These commands does not require statement terminator and applicable to the sessions , those will be automatically cleared when session was closed.
LINESIZE
This will be used to set the linesize. Default linesize is 80.
Syntax:
Set linesize
Ex:
SQL> set linesize 100
PAGESIZE
This will be used to set the pagesize. Default pagesize is 14.
Syntax:
Set pagesize
Ex:
SQL> set pagesize 30
DESCRIBE
This will be used to see the object’s structure.
Syntax:
Describe or desc
Ex:
SQL> desc dept
Name Null? Type
----------------------------------------------------------------- ---------------------
DEPTNO NOT NULL NUMBER(2)
DNAME VARCHAR2(14)
LOC VARCHAR2(13)
PAUSE
When the displayed data contains hundreds or thousands of lines, when you select it then it will automatically scrolls and displays the last page data. To prevent this you can use this pause option. By using this it will display the data correspoinding to the pagesize with a break which will continue by hitting the return key. By default this will be off.
Syntax:
Set pause on | off
Ex:
SQL> set pause on
FEEDBACK
This will give the information regarding howmany rows you selected the object. By default the feedback message will be displayed, only when the object contains more than 5 rows.
Syntax:
Set feedback
Ex:
SQL> set feedback 4
SQL> select * from dept;
DEPTNO DNAME LOC
---------- -------------- -------------
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON
4 rows selected.
HEADING
If you want to display data without headings, then you can achieve with this. By default heading is on.
Syntax:
Set heading on | off
Ex:
SQL> set heading off
SQL> select * from dept;
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON
SERVEROUTPUT
This will be used to display the output of the PL/SQL programs. By default this will be off.
Syntax:
Set serveroutput on | off
Ex:
SQL> set serveroutput on
TIME
This will be used to display the time. By default this will be off.
Syntax:
Set time on | off
Ex:
SQL> set time on
19:56:33 SQL>
TIMING
This will give the time taken to execute the current SQL statement. By default this will be off.
Syntax:
Set timing on | off
Ex:
SQL> set timing on
SQL> select * from dept;
DEPTNO DNAME LOC
---------- -------------- -------------
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON
Elapsed: 00:00:00.06
SQLPROMPT
This will be used to change the SQL prompt.
Syntax:
Set sqlprompt
Ex:
SQL> set sqlprompt 'ORACLE>'
ORACLE>
SQLCASE
This will be used to change the case of the SQL statements. By default the case is mixed.
Syntax:
Set sqlcase upper | mixed | lower
Ex:
SQL> set sqlcase upper
SQLTERMINATOR
This will be used to change the terminator of the SQL statements. By default the terminator is ;.
Syntax:
Set sqlterminator
Ex:
SQL> set sqlterminator :
SQL> select * from dept:
DEFINE
By default if the & character finds then it will treat as bind variable and ask for the input. Suppose your want to treat it as a normal character while inserting data, then you can prevent this by using the define option. By default this will be on
Syntax:
Set define on | off
Ex:
SQL>insert into dept values(50,'R&D','HYD');
Enter value for d:
old 1: insert into dept values(50,'R&D','HYD')
new 1: INSERT INTO DEPT VALUES(50,'R','HYD')
SQL> set define off
SQL>insert into dept values(50,'R&D','HYD'); -- here it won’t ask for value
NEWPAGE
This will shows how many blank lines will be left before the report. By default it will leave one blank line.
Syntax:
Set newpage
Ex:
SQL> set newpage 10
The zero value for newpage does not produce zero blank lines instead it switches to a special property which produces a top-of-form character (hex 13) just before the date on each page. Most modern printers respond to this by moving immediately to the top of the next page, where the priting of the report will begin.
HEADSEP
This allow you to indicate where you want to break a page title or a column heading that runs longer than one line. The default heading separator is vertical bar (|).
Syntax:
Set headsep
Ex:
SQL> select * from dept;
DEPTNO DNAME LOC
---------- -------------- -------------
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON
SQL> set headsetp !
SQL> col dname heading 'DEPARTMENT ! NAME'
SQL> /
DEPARTMENT
DEPTNO NAME LOC
---------- ----------------- ----------
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON
ECHO
When using a bind variable, the SQL statement is maintained by echo. By default this is off.
Syntax:
Set echo on | off
VERIFY
When using a bind variable, the old and new statements will be maintained by verify. By default this is on.
Syntax:
Set verify on | off
Ex:
SQL> select * from dept where deptno = &dno;
Enter value for dno: 10
old 1: select * from dept where deptno = &dno
new 1: select * from dept where deptno = 10
DEPTNO DNAME LOC
---------- ---------------- -----------
10 ACCOUNTING NEW YORK
SQL> set verify off
SQL> select * from dept where deptno = &dno;
Enter value for dno: 20
DEPTNO DNAME LOC
---------- ------------- -----------
20 RESEARCH DALLAS
PNO
This will give displays the page numbers. By default the value would be zero.
Ex:
SQL> col hiredate new_value xtoday noprint format a1 trunc
SQL> ttitle left xtoday right 'page' sql.pno
SQL> select * from emp where deptno = 10;
09-JUN-81 page 1
EMPNO ENAME JOB MGR SAL COMM DEPTNO
---------- ---------- --------------- --------- ----- ---------- ----------
7782 CLARK MANAGER 7839 2450 10
7839 KING PRESIDENT 5000 10
7934 MILLER CLERK 7782 1300 10
In the above noprint tells SQLPLUS not to display this column when it prints the results of the SQL statement. Dates that have been reformatted by TO_CHAR get a default width of about 100 characters. By changing the format to a1 trunc, you minimize this effect. NEW_VALUE inserts contents of the column retrieved by the SQL statement into a variable called xtoday.
SPECIAL FILES
LOGIN.sql
If you would like SQLPLUS to define your own environmental settings, put all the required commands in a file named login.sql. This is a special filename that SQLPLUS always looks for whenever it starts up. If it finds login.sql, it executes any commands in it as if you had entered then by hand. You can put any command in login.sql that you can use in SQLPLUS, including SQLPLUS commands and SQL statements. All ot them executed before SQLPLUS gives you the SQL> prompt.
GLOGIN.sql
This is used in the same ways as LOGIN.sql but to establish default SQLPLUS settings for all users of a database.
IMP QUERIES
1) To find the nth row of a table
SQL> Select *from emp where rowid = (select max(rowid) from emp where rownum <= 4);
Or
SQL> Select *from emp where rownum <= 4 minus select *from emp where rownum <= 3;
2) To find duplicate rows
SQL> Select *from emp where rowid in (select max(rowid) from emp group by empno,
ename, mgr, job, hiredate, comm, deptno, sal);
Or
SQL> Select empno,ename,sal,job,hiredate,comm , count(*) from emp group by
empno,ename,sal,job,hiredate,comm having count(*) >=1;
3) To delete duplicate rows
SQL> Delete emp where rowid in (select max(rowid) from emp group by
empno,ename,mgr,job,hiredate,sal,comm,deptno);
4) To find the count of duplicate rows
SQL> Select ename, count(*) from emp group by ename having count(*) >= 1;
5) How to display alternative rows in a table?
SQL> select *from emp where (rowid,0) in (select rowid,mod(rownum,2) from emp);
6) Getting employee details of each department who is drawing maximum sal?
SQL> select *from emp where (deptno,sal) in
( select deptno,max(sal) from emp group by deptno);
7) How to get number of employees in each department , in which department is having more than 2500 employees?
SQL> Select deptno,count(*) from emp group by deptno having count(*) >2500;
8) To reset the time to the beginning of the day
SQL> Select to_char(trunc(sysdate),’dd-mon-yyyy hh:mi:ss am’) from dual;
9) To find nth maximum sal
SQL> Select *from emp where sal in (select max(sal) from (select *from emp order by sal)
where rownum <= 5);
INTRODUCTION
CHARACTERSTICS
Highly structured, readable and accessible language.
Standard and Protable language.
Embedded language.
Improved execution authority.
10g FEATURES
Optimized compiler
.
To change the optimizer settings for the entire database, set the database parameter
PLSQL_OPTIMIZE_LEVEL. Valid settings are as follows
0 - No optimization
1 - Moderate optimization
2 - Aggressive optimization
These settings are also modifiable for the current session.
SQL> alter session set plsql_optimze_level=2;
Oracle retains optimizer settings on a module-by-module basis. When you recompile a particular module with nondefault settings, the settings will stick allowing you to recompile later on using REUSE SETTINGS.
SQL> Alter procedure proc compile plsql_optimize_level=1;
SQL> Alter procedure proc compile reuse settings;
Compile-time warnings.
Starting with oracle database 10g release 1 you can enable additional compile-time warnings to help make your programs more robust. The compiler can detect potential runtime problems with your code, such as identifying lines of code that will never be run. This process, also known as lint checking.
To enable these warnings fo the entire database, set the database parameter PLSQL_WARNINGS. These settings are also modifiable for the current session.
SQL> alter session set plsql_warnings = ‘enable:all’;
The above can be achieved using the built-in package DBMS_WARNING.
Conditional compilation.
Conditional compilation allows the compiler to allow to compile selected parts of a program based on conditions you provide with the $IF directive.
Support for non-sequential collections in FORALL.
Improved datatype support.
Backtrace an exception to its line number.
When handling an error, how can you find the line number on which the error was originally raised?
In earlier release, the only way to do this was allow you exception to go unhandled and then view the full error trace stack.
Now you can call DBMS_UTILITY.FORMAT_ERROR_BACKTRACE function to obtain that stack and manipulate it programmatically within your program.
Set operators for nested tables.
Support for regular expressions.
Oracle database 10g supports the use of regular expressions inside PL/SQL code via four new built-in functions.
REGEXP_LIKE
REGEXP_INSTR
REGEXP_SUBSTR
REGEXP_REPLACE
Programmer-defined quoting mechanism.
Starting with oracle database 10g release 1, you can define your own quoting mechanism for string literals in both SQL and PL/SQL.
Use the characters q’(q followed by a single quote) to note the programmer-defined deliemeter for you string literal.
Ex:
DECLARE
v varchar(10) := 'computer';
BEGIN
dbms_output.put_line(q'*v = *' || v);
dbms_output.put_line(q'$v = $' || v);
END;
Output:
v = computer
v = computer
Many new built-in packages.
DBMS_SCHEDULER
Represents a major update to DBMS_JOB. DBMS_SCHEDULER provides much improved functionality for scheduling and executing jobs defined via stored procedures.
DBMS_CRYPTO
Offers the ability to encrypt and decrypt common oracle datatype, including RAWs, BLOBs, and CLOBs. It also provides globalization support for encrypting data across different charactersets.
DBMS_MONITOR
Provides an API to control additional tracing and statistics gathering of sessions.
DBMS_WARNING
Provides an API into the PL/SQL compiler warnings module, allowing you to read and change settings that control which warnings are suppressed, displayed, or treated as errors.
STANDARD PACKAGE
Oracle has defined in this special package. Oracle defines quite a few identifiers in this package, including built-in exceptions, functions and subtypes.
You can reference the built-in form by prefixing it with STANDARD.
The basic unit in any PL/SQL program is block. All PL/SQL programs are composed of blocks which can occur sequentially or nested.
BLOCK STRUCTURE
Declare
-- declarative section
Begin
-- executable section
Exception
-- exception section
End;
In the above declarative and exceptiona sections are optional.
BLOCK TYPES
Anonymous blocks
Named blocks
Labeled blocks
Subprograms
Triggers
ANONYMOUS BLOCKS
Anonymous blocks implies basic block structure.
Ex:
BEGIN
Dbms_output.put_line(‘My first program’):
END;
LABELED BLOCKS
Labeled blocks are anonymous blocks with a label which gives a name to the block.
Ex:
<
BEGIN
Dbms_output.put_line(‘My first program’):
END;
SUBPROGRAMS
Subprograms are procedures and functions. They can be stored in the database as stand-alone objects, as part of package or as methods of an object type.
TRIGGERS
Triggers consists of a PL/SQL block that is associated with an event that occur in the database.
NESTED BLOCKS
A block can be nested within the executable or exception section of an outer block.
IDENTIFIERS
Identifiers are used to name PL/SQL objects, such as variables, cursors, types and subprograms. Identifiers consists of a letter, optionally followed by any sequence of characters, including letters, numbers, dollar signs, underscores, and pound signs only. The maximum length for an identifier is 30 characters.
QUOTED IDENTIFIERS
If you want to make an identifier case sensitive, include characters such as spaces or use a reserved word, you can enclose the identifier in double quotation marks.
Ex:
DECLARE
"a" number := 5;
"A" number := 6;
BEGIN
dbms_output.put_line('a = ' || a);
dbms_output.put_line('A = ' || A);
END;
Output:
a = 6
A = 6
COMMENTS
Comments improve readability and make your program more understandable. They are ignored by the PL/SQL compiler. There are two types of comments available.
Single line comments
Multiline comments
SINGLE LINE COMMENTS
A single-line comment can start any point on a line with two dashes and continues until the end of the line.
Ex:
BEGIN
Dbms_output.put_line(‘hello’); -- sample program
END;
MULTILINE COMMENTS
Multiline comments start with the /* delimiter and ends with */ delimiter.
Ex:
BEGIN
Dbms_output.put_line(‘hello’); /* sample program */
END;
VARIABLE DECLERATIONS
Variables can be declared in declarative section of the block;
Ex:
DECLARE
a number;
b number := 5;
c number default 6;
CONSTANT DECLERATIONS
To declare a constant, you include the CONSTANT keyword, and you must supply a default value.
Ex:
DECLARE
b constant number := 5;
c constant number default 6;
NOT NULL CLAUSE
You can also specify that the variable must be not null.
Ex:
DECLARE
b constant number not null:= 5;
c number not null default 6;
ANCHORED DECLERATIONS
PL/SQL offers two kinds of achoring.
Scalar anchoring
Record anchoring
SCALAR ANCHORING
Use the %TYPE attribute to define your variable based on table’s column of some other PL/SQL scalar variable.
Ex:
DECLARE
dno dept.deptno%type;
Subtype t_number is number;
a t_number;
Subtype t_sno is student.sno%type;
V_sno t_sno;
RECORD ANCHORING
Use the %ROWTYPE attribute to define your record structure based on a table.
Ex:
DECLARE
V_dept dept%rowtype;
BENEFITS OF ANCHORED DECLARATIONS
Synchronization with database columns.
Normalization of local variables.
PROGRAMMER-DEFINED TYPES
With the SUBTYPE statement, PL/SQL allows you to define your own subtypes or aliases of predefined datatypes, sometimes referred to as abstract datatypes.
There are two kinds of subtypes.
Constrained
Unconstrained
CONSTRAINED SUBTYPE
A subtype that restricts or constrains the values normally allowd by the datatype itself.
Ex:
Subtype positive is binary_integer range 1..2147483647;
In the above declaration a variable that is declared as positive can store only ingeger greater than zero even though binary_integer ranges from -2147483647..+2147483647.
UNCONSTRAINED SUBTYPE
A subtype that does not restrict the values of the original datatype in variables declared with the subtype.
Ex:
Subtype float is number;
DATATYPE CONVERSIONS
PL/SQL can handle conversions between different families among the datatypes.
Conversion can be done in two ways.
Explicit conversion
Implicit conversion
EXPLICIT CONVERSION
This can be done using the built-in functions available.
IMPLICIT CONVERSION
PL/SQL will automatically convert between datatype families when possible.
Ex:
DECLARE
a varchar(10);
BEGIN
select deptno into a from dept where dname='ACCOUNTING';
END;
In the above variable a is char type and deptno is number type even though, oracle will automatically converts the numeric data into char type assigns to the variable.
PL/SQL can automatically convert between
Characters and numbers
Characters and dates
VARIABLE SCOPE AND VISIBILITY
The scope of a variable is the portion of the program in which the variable can be accessed. For PL/SQL variables, this is from the variable declaration until the end of the block. When a variable goes out of scope, the PL/SQL engine will free the memory used to store the variable.
The visibility of a variable is the portion of the program where the variable can be accessed without having to qualify the reference. The visibility is always within the scope. If it is out of scope, it is not visible.
Ex1:
DECLARE
a number; -- scope of a
BEGIN
--------
DECLARE
b number; -- scope of b
BEGIN
-----
END;
------
END;
Ex2:
DECLARE
a number;
b number;
BEGIN
-- a , b available here
DECLARE
b char(10);
BEGIN
-- a and char type b is available here
END;
-----
END;
Ex3:
<
DECLARE
a number;
b number;
BEGIN
-- a , b available here
DECLARE
b char(10);
BEGIN
-- a and char type b is available here
-- number type b is available using <
END;
------
END;
PL/SQL CONTROL STRUCTURES
PL/SQL has a variety of control structures that allow you to control the behaviour of the block as it runs. These structures include conditional statements and loops.
If-then-else
Case
Case with no else
Labeled case
Searched case
Simple loop
While loop
For loop
Goto and Labels
IF-THEN-ELSE
Syntax:
If
Sequence of statements;
Elsif
Sequence of statements;
……
Else
Sequence of statements;
End if;
Ex:
DECLARE
dno number(2);
BEGIN
select deptno into dno from dept where dname = 'ACCOUNTING';
if dno = 10 then
dbms_output.put_line('Location is NEW YORK');
elsif dno = 20 then
dbms_output.put_line('Location is DALLAS');
elsif dno = 30 then
dbms_output.put_line('Location is CHICAGO');
else
dbms_output.put_line('Location is BOSTON');
end if;
END;
Output:
Location is NEW YORK
CASE
Syntax:
Case test-variable
When value1 then sequence of statements;
When value2 then sequence of statements;
……
When valuen then sequence of statements;
Else sequence of statements;
End case;
Ex:
DECLARE
dno number(2);
BEGIN
select deptno into dno from dept where dname = 'ACCOUNTING';
case dno
when 10 then
dbms_output.put_line('Location is NEW YORK');
when 20 then
dbms_output.put_line('Location is DALLAS');
when 30 then
dbms_output.put_line('Location is CHICAGO');
else
dbms_output.put_line('Location is BOSTON');
end case;
END;
Output:
Location is NEW YORK
CASE WITHOUT ELSE
Syntax:
Case test-variable
When value1 then sequence of statements;
When value2 then sequence of statements;
……
When valuen then sequence of statements;
End case;
Ex:
DECLARE
dno number(2);
BEGIN
select deptno into dno from dept where dname = 'ACCOUNTING';
case dno
when 10 then
dbms_output.put_line('Location is NEW YORK');
when 20 then
dbms_output.put_line('Location is DALLAS');
when 30 then
dbms_output.put_line('Location is CHICAGO');
when 40 then
dbms_output.put_line('Location is BOSTON');
end case;
END;
Output:
Location is NEW YORK
LABELED CASE
Syntax:
<
