Triggers
For those programmers who pride themselves on their laziness, triggers are a wonderful thing. By creating a trigger you can get maximum effect with minimum effort.
Triggers are activated by an INSERT, DELETE, or UPDATE SQL statement. They are often used to maintain referential integrity and avoid orphaned records—for example, deleting an invoice might well trigger deletion of all related invoice items. We're going to create three triggers for our application: one to mimic a timestamp field, another to show the advantages of laziness, and finally a trigger to demonstrate how a view can be "updated."
The timestamp triggers are shown in Listing 15-3. They are activated whenever a record in the tblresources table is added or updated.
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