C H A P T E R  15

Triggers

Now that you have become quite proficient in using SQL Server 2012, you ought to know about one last aspect of it. Triggers are that one last step, and this chapter is the missing link in the foundation of your knowledge and skill set.

At times a modification to data somewhere within your database will require an automatic action on data elsewhere, either in your database, another database, or elsewhere within SQL Server; a trigger is the object that will do this for you. When a modification to your data occurs, SQL Server will fire a trigger, which is a specialized stored procedure that will run, performing the actions that you desire. Triggers are similar to constraints but more powerful, and they require more system overhead, which can lead to a reduction in performance. Triggers are most commonly used to perform business rules validation, carry out cascading data modifications (changes on one table causing changes to be made on other tables), and keep track of change....Chapter 3