Josh, Thanks for the info.
I need to change an insert into an update when the key already exists. I have been using a rules to test it on a small set (table) and it works. "Rules can't use indexes" just scared me. I will have to test on a larger set. Also, I had the impression that if a trigger returned NULL, one would get the equivalent of "DO NOTHING". Am I wrong with that assumption? JLL Josh Berkus wrote: > > Bruce, Richard, > > > Triggers are mostly for testing/modifying the row being > > inserted/updated, while rules are better for affecting other rows or > > other tables. > > Hmmm. Thought that there were also some other criteria: > > 1) Rules can't use indexes to do their processing, so Rules which query large > secondary tables can be a bad idea (maybe this has changed?) > > 2) Only Rules can "DO INSTEAD"; thus, only Rules are good for defining > Read/Write views. > > 3) There are no AFTER Rules, making, for example, a rule with a table check on > the new data impractical, so you'd want to use Triggers or Constraints > > etc. > > There are, IMHO, some things Rules are better for, and some things Triggers > are better for. I tend to use all Triggers except for updatable views, > simply because using a mix of Rules and Triggers can be very hard to keep > track of, but YMMV. > > -- > -Josh Berkus > Aglio Database Solutions > San Francisco ---------------------------(end of broadcast)--------------------------- TIP 1: subscribe and unsubscribe commands go to [EMAIL PROTECTED]
