ALTER clause is one of the DDL commands which allows you to change object structure in database like table, stored procedure, trigger, or any other object in the database. By using ALTER command you can add or remove columns in a table, you can add and remove index from a table as well as you can update a stored procedure. ALTER command is an essential SQL commands for programmers similar to SELECT, UPDATE, and DELETE. If you know how to create a table or index then you should also know how to modify a table or index using ALTER command. In this article, we'll see some common ALTER table examples in SQL to learn this command better and become a better database developer.