Monday, 30 July 2007

The order of triggers...

It was always considered bad design to design a system which relied on the order of the same type of triggers, i.e.
having two BEFORE UPDATE triggers where trigger 2 relied on trigger 1 having fired. The reason for this is that Oracle doesn't guarantee the order in which these two triggers should fire. Sure, BEFORE UPDATE trigger(s) will fire before AFTER UPDATE trigger(s), but two BEFORE UPDATE triggers can fire in any order.

Well, along come Oracle again and rewrite the rulebook, well.. sort of. As part of 11g, the trigger definition can now contain the FOLLOWS keyword, which takes an argument of a trigger name. This keyword allows you to specify a trigger which this trigger is guaranteed fire after (i.e. this trigger follows another...).

I've updated the trigger firing sequence section of the main site to include a mention of this and a reference to the above page.

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