• Timing of action
execution: before, after or instead of triggering
event
• The action can
refer to both the old and new state of the database.
•
• Update events may
specify a particular column or set of columns.
•
• A condition is
specified with a WHEN clause.
•
• The action can be
performed either for
• once for every
tuple, or
• once for all the
tuples that are changed by the database operation.