[dba-SQLServer] Enforcing a rule

Besdies ensuring data consistency, triggers are often used for maintaining
an audit trail. On an insert it doesn't make much sense, but on update and
delete it does (you can write the old row to a table before doing the actual
update, or write the old row to a table before doing the delete). IIRC,
Susan and I wrote about that some time ago in TechRepublic.

Arthur