One aspect of triggers that can be difficult to understand is the order in which triggers fire if several triggers are impacted by the same triggering action. Whether competing triggers are fired, and the order in which they are fired, depends on two things: trigger type (BEFORE, INSTEAD OF, or AFTER), and trigger scope (row-level or statement-level).
For row-level triggers, BEFORE triggers fire before INSTEAD OF triggers, which fire before AFTER triggers. All row-level triggers for a given row fire before any triggers fire for a subsequent row.
For statement-level triggers, INSTEAD OF triggers fire before AFTER triggers. Statement-level BEFORE triggers are not supported.
If there are competing statement-level and row-level AFTER triggers, the statement-level AFTER triggers fire after all row-level triggers have completed.
If there are competing statement-level and row-level INSTEAD OF triggers, the row-level triggers do not fire.
INSTEAD OF triggers