SQL Commands....Contd

Alter Table Command

We can change structure of a table (adding or removing columns) using DDL Command

1. ALTER TABLE

Adding columns to existing table
Syntax:
ALTER TABLE <table name> ADD (<column name> data type [Column
constraints]);
Example: Altering the above table by adding new columns, mark1 and mark2.
Alter table student add (mark1 int);
Alter table student add (mark2 int2 not null);
To Modify an existing column
Syntax:
ALTER TABLE <table name> MODIFY(<Column Name> <new data type> [(<new size>));

Eg:- ALTER TABLE student MODIFY( division int);

2.  Drop Table Command
We can delete a table using DDL command DROP TABLE

This Command is used to delete a table from database
E.g.: drop table student;