From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Don Isgitt <djisgitt(at)soundenergy(dot)com> |
Cc: | postgresql general <pgsql-general(at)postgresql(dot)org> |
Subject: | Re: Update sql question |
Date: | 2005-06-07 16:49:44 |
Message-ID: | 9645.1118162984@sss.pgh.pa.us |
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Lists: | pgsql-general |
Don Isgitt <djisgitt(at)soundenergy(dot)com> writes:
> Tom Lane wrote:
>> BTW, I find the "limit 1" a bit scary --- if there are multiple matches,
>> this coding will select a random one of them. Is that really what you
>> want?
> Ah, quite so. Thank you, Tom and Richard for your spot on help. Tom, I
> appreciate your concern for my limit 1; I confess it is a lazy way out.
> There are many multiple duplicate entries (oldopr and newopr), so rather
> than cleaning up the table, ...
Perhaps write the sub-select as
(select distinct newopr from opr_match
where state=master.state and oldopr=master.operator)
so that you'll get an error if there's more than one value for newopr in
the table. I'm not sure what performance hit you'll take, but checking
the data for self-consistency is a good idea in my book, especially when
you already know it's not very clean ...
regards, tom lane
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