| From: | Richard Huxton <dev(at)archonet(dot)com> |
|---|---|
| To: | "Zuev Dmitry" <envoy1(at)chat(dot)ru>, pgsql-sql(at)postgresql(dot)org |
| Subject: | Re: help on sql query |
| Date: | 2002-11-26 15:26:37 |
| Message-ID: | 200211261526.37984.dev@archonet.com |
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| Lists: | pgsql-sql |
On Tuesday 26 Nov 2002 1:14 pm, Zuev Dmitry wrote:
> Suppose you have a table T:
>
> A B
> 1 '111'
> 2 '222'
>
> How do you select A and B of the record with A maximum?
> 1) SELECT A, B FROM T ORDER BY A DESC LIMIT 1
>
> 2) SELECT A, B FROM T WHERE A IN (SELECT MAX(A) FROM T)
>
> What do yo think of the queries above? And give me the better
> implementation if possible.
If you have an index on A the first option will be faster. All PG has to do in
this case is check the end of the index and fetch one row.
--
Richard Huxton
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