From: | Jean-Luc Lachance <jllachan(at)nsd(dot)ca> |
---|---|
To: | Darren Ferguson <darren(at)crystalballinc(dot)com> |
Cc: | Jean-Christian Imbeault <jc(at)mega-bucks(dot)co(dot)jp>, pgsql-general <pgsql-general(at)postgresql(dot)org> |
Subject: | Re: IN vs EXIIST |
Date: | 2002-09-19 17:57:14 |
Message-ID: | 3D8A0FFA.B1FEF32A@nsd.ca |
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Thread: | |
Lists: | pgsql-general |
This is not what he wants.
He wants all keys that have only true for x.
> Why areyou using the sub select. If you just want all the key1 where x is
> true then the following will work
>
> SELECT DISTINCT(key1) FROM a WHERE x = TRUE;
>
> If you want all rows and don't care about duplicates then remove the
> distinct.
>
> Hope this helps
>
> >
> > I've seen many posts saying that using IN is not optimal and replacing
> > it with EXISTS is much better. I've read the only docs but I can't
> > understand the difference between the two or how to convert.
> >
> > Can someone point me to some other docs or explain to me how to convert?
> > Or is my table schema wrong?
> >
> > Thanks!
> >
> > Jc
> >
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