Home page
 
 Home 
 ASP 
 PHP 
 SQL 
 HTML 
 JavaScript 
 Search 
 Contact 
 
Search
or browse popular tags
Subscription

Sign up for the free email newsletter for new tips, tutorials and more. Enter your email address below, and then click the button.

Privacy Policy

RSS Twitter

SQL: ALTER TABLE

Print

The ALTER TABLE statement allows to change the structure of a table after it has been created. New columns can be added with the ADD clause. Existing columns may be removed from a table using the Drop clause.

The syntax of the ALTER TABLE statement is as follows:

ALTER TABLE table_name
ADD column_name data_type

ALTER TABLE table_name
DROP COLUMN column_name

Note: The ALTER TABLE statement is not part of ANSI/ISO standard. This means that all the commercial dialects of SQL implement different clauses and command syntax.

Example #1

ALTER TABLE Orders
ADD Quantity SMALLINT 

This example adds a single column to the "Orders" table by specifying the new column name and data type.

Example #2

ALTER TABLE EmployeeAddressTable
ADD Description VARCHAR(20) DEFAULT 'USA' NOT NULL

This example adds a column named "Description" to the "EmployeeAddressTable" table. We also add the reserved words NOT NULL to require valid data to be added to that column and specify a default value.

Example #3

ALTER TABLE AntiqueOwners DROP COLUMN State

This example drops the "State" column from the "AntiqueOwners" table.




Tags:

Add To: Add to dzone dzone | Digg this digg | Add to del.icio.us del.icio.us | Stumble it stumbleupon

  • Comments





Copyright © 2005-2023             www.WebCheatSheet.com All Rights Reserved.