| From: | Mike Christensen <mike(at)kitchenpc(dot)com> |
|---|---|
| To: | Simon Riggs <simon(at)2ndquadrant(dot)com>, pgsql-general(at)postgresql(dot)org |
| Subject: | Re: Constraint to ensure value does NOT exist in another table? |
| Date: | 2011-06-16 06:50:11 |
| Message-ID: | BANLkTi=Ys4mRchmLk7nGf3=-0ww+h5J2_A@mail.gmail.com |
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| Thread: | |
| Lists: | pgsql-general |
>> I know I can setup a FK constraint to make sure Table1.ColA exists in
>> Table2.Key, however what if I want to do the reverse?
>>
>> I want to ensure Table1.ColA does NOT exist in Table2.Key.. Can I do
>> this with any sort of CHECK constraint, trigger, custom function, etc?
>
>
> The most common constraints are provided for, but then after that you
> have to use triggers.
>
> PostgreSQL deliberately doesn't support queries in CHECK constraints
> for this reason.
Thanks! I wrote a Trigger for this and it seems to work fairly well..
I kinda figured that was the obvious way, but thought there might be
some new 9.x feature that made this sort of thing possible.
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