From: | Josh Berkus <josh(at)agliodbs(dot)com> |
---|---|
To: | Thrasher <thrasher(at)fibers(dot)upc(dot)es> |
Cc: | pgsql-sql(at)postgresql(dot)org |
Subject: | Re: Unique constraint over null values |
Date: | 2002-09-30 17:50:05 |
Message-ID: | 200209301050.05473.josh@agliodbs.com |
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Thread: | |
Lists: | pgsql-sql |
Thrasher,
> I think I'll follow your advice, as this is the method that I had in my
> pocket to use if I had no response. I tried with TRIM and other
> functions in the CHECK constraint, but I guess that I cannot use
> functions over a check field.
>
> It surprised me, but anyway, I'll do that.
>
> Thanks a lot for your prompt reply
No problem. You should also add a second constraint:
CHECK ((type = 'x' AND data2 <> 'blank value') OR (type = 'y' AND data2 =
'blank value'))
To enforce your other criterion.
Keeop in mind that depending on the rest of your data structure, there are
probably 8 different ways to approach this problem. I'd reccomend, in fact,
a quick reading of Pascal's "Practical Issues in Database Management" on
normalization to see the different table structures that might work for you.
--
-Josh Berkus
Aglio Database Solutions
San Francisco
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