Table of Contents

    SQL ALTER TABLE Statement: A Comprehensive Guide

    SQL ALTER TABLE Statement: A Comprehensive Guide

    The ALTER TABLE statement is used to add, delete, or modify columns in an existing table.

    The ALTER TABLE statement is also used to add and drop various constraints on an existing table.

    Syntax:To add a column in a table, use the following syntax:

    
    ALTER TABLE table_name
    ADD column_name datatype;
    

    Syntax: ALTER TABLE - DROP COLUMN

    
    ALTER TABLE table_name
    DROP COLUMN column_name;
    

    ALTER TABLE - ALTER/MODIFY COLUMN

    Syntax: SQL Server / MS Access:

    
    ALTER TABLE table_name
    ALTER COLUMN column_name datatype;
    

    Syntax: My SQL / Oracle (prior version 10G):

    
    ALTER TABLE table_name
    MODIFY COLUMN column_name datatype;
    

    Syntax: Oracle 10G and later:

    
    ALTER TABLE table_name
    MODIFY column_name datatype;