| From: | Albert Reiner <e8901869(at)student(dot)tuwien(dot)ac(dot)at> |
|---|---|
| To: | Murray Hobbs <murray(at)efone(dot)com> |
| Cc: | pgsql-sql(at)postgresql(dot)org, pgsql-novice(at)postgresql(dot)org, pgsql-general(at)postgresql(dot)org |
| Subject: | Re: [NOVICE] protected ON DELETE CASCADE |
| Date: | 2001-08-23 12:12:32 |
| Message-ID: | Pine.HPX.4.10.10108231409210.15991-100000@stud3.tuwien.ac.at |
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| Thread: | |
| Lists: | pgsql-general pgsql-novice pgsql-sql |
On Thu, 23 Aug 2001, Murray Hobbs wrote:
> A <- B
> A <- C <- D
>
> i want to maintain integrity so that if A is deleted from then so is
> anything referencing from B and C - no problem ON DELETE CASCADE
>
> but if there are any D's that point back to A (through composite key in
> C) i don't want the delete to go ahead - at all - i want an error
> message and condition
what about ON DELETE RESTRICT there?
> I've looked at TRIGGER but then i'm writing a function (in SQL?) which
> is called by a trigger - again - how do i confirm or reject a delete?
Look at the docs: there is a difference between DO and DO INSTEAD (I
think, I am no expert on Pg, and I do not have access to a Pg system right
now).
Albert.
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