Using INSTEAD OF Triggers

INSTEAD OF triggers override the standard actions of the triggering statement: an INSERT, UPDATE, or DELETE. An INSTEAD OF trigger can be defined to perform error or value checking on one or more columns, and then perform additional actions before inserting the record. For example, when the value being updated in an hourly wage column in a payroll table exceeds a specified value, a trigger can be defined to either produce an error message and roll back the transaction, or insert a new record into an audit trail before inserting the record into the payroll table. For more information, see Designing INSTEAD OF Triggers.

INSTEAD OF triggers can be defined on either tables or views; however, INSTEAD OF triggers are most useful for extending the types of updates a view can support. For example, INSTEAD OF triggers can provide the logic to modify multiple base tables through a view or to modify base tables that contain the following columns:

• timestamp data type

• Computed columns

• Identity columns

The following topics explain how to use INSTEAD OF Triggers in more detail:

• INSTEAD OF INSERT Triggers

• INSTEAD OF UPDATE Triggers

• INSTEAD OF DELETE Triggers

• Expressions and Computed Columns in INSTEAD OF Triggers

• Using text, ntext, and image Data in INSTEAD OF Triggers

See Also

Concepts

Designing DML Triggers

Implementing DML Triggers