Alter Table (SQL)
Alter - To modify an existing database object.
An ALTER statement in SQL changes the properties of an object inside of a relational database management system (RDBMS). The types of objects that can be altered depends on which RDBMS is being used. The typical usage is:
ALTER objecttype objectname parameters.
For example, the command to add (then remove) a column named bubbles for an existing table named sink would be:
ALTER TABLE sink ADD bubbles INTEGER; ALTER TABLE sink DROP COLUMN bubbles;
Content extracted from free documentation.