SQL LEARNING CLASS1

INTRODUCTION

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 <table_name> (col1 datatype1, col2 datatype2 …coln datatypen);

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 <table_name) values (value1, value2, value3 …. Valuen);

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 <table_name) values (&col1, &col2, &col3 …. &coln);

This will prompt you for the values but for every insert you have to use forward slash.

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 <table_name)(col1, col2, col3 … Coln) values (value1, value2, value3 ….

Valuen);

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 <table_name)(col1, col2, col3 … coln) values (&col1, &col2, &col3 …. &coln);

This will prompt you for the values but for every insert you have to use forward slash.

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 <table_name>; -- here * indicates all columns

or

Select col1, col2, … coln from <table_name>;

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 <table_name> where <condition>;

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 <table_name> where <condition1> and <condition2> and .. <conditionn>;

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 <table_name> where <condition1> and <condition2> or .. <conditionn>;

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 <table_name> where <col> between <lower bound> and <upper bound>;

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 <table_name> where <col> not between <lower bound> and <upper bound>;

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 <table_name> where <col> in ( value1, value2, value3 … valuen);

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 <table_name> where <col> not in ( value1, value2, value3 … valuen);

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 <table_name> where <col> is null;

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 <table_name> where <col> is not null;

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 <table_name> where <col> like <pattern>;

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 <table_name> order by <col> desc;

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 <table_name> set <col1> = value1, <col2> = value2 where <condition>;

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 <table_name> where <condition>;

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 <table_name> add <col datatype>;

Ex:

SQL> alter table student add sdob date;

b) REMOVING COLUMN

Syntax:

alter table <table_name> drop <col datatype>;

Ex:

SQL> alter table student drop column sdob;

c) INCREASING OR DECREASING PRECISION OF A COLUMN

Syntax:

alter table <table_name> modify <col datatype>;

Ex:

SQL> alter table student modify marks number(5);

* To decrease precision the column should be empty.

d) MAKING COLUMN UNUSED

Syntax:

alter table <table_name> set unused column <col>;

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 <table_name> drop unused columns;

Ex:

SQL> alter table student drop unused columns;

* You can not drop individual unused columns of a table.

e) RENAMING COLUMN

Syntax:

alter table <table_name> rename column <old_col_name> to <new_col_name>;

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 <table_name>;

Ex:

SQL> truncate table student;

USING DROP

This will be used to drop the database object;

Syntax:

Drop table <table_name>;

Ex:

SQL> drop table student;

USING RENAME

This will be used to rename the database object;

Syntax:

rename <old_table_name> to <new_table_name>;

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 <savepoint_name>;

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 <privileges> on <object_name> to <user_name> [with grant option];

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 <privileges> on <object_name> from <user_name>;

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