A trigger is a sort of stored procedure that executes automatically when a database server event occurs. When a user attempts to edit data via a data manipulation language (DML) event, DML triggers are triggered. INSERT, UPDATE, and DELETE statements on a table or view are DML events. Data definition language (DDL) triggers are run in response to a range of DDL events. The CREATE, ALTER, and DROP statements in Transact-SQL, as well as some system stored procedures that perform DDL-like actions, are the most common triggers for these events.
Triggers are used to maintain data integrity by checking or modifying data in a consistent manner. A trigger is a collection of SQL statements that can be used by many applications. When numerous programs need to do the same database operation, it allows you to avoid writing redundant code.