Re: Re: Does PostgreSQL support EXISTS?

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От Bruce Momjian
Тема Re: Re: Does PostgreSQL support EXISTS?
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Msg-id 200106131403.f5DE3Pr03671@candle.pha.pa.us
обсуждение исходный текст
Ответ на Re: Re: Does PostgreSQL support EXISTS?  (Michael Meskes <meskes@postgresql.org>)
Ответы Re: Re: Does PostgreSQL support EXISTS?  (Tom Lane <tgl@sss.pgh.pa.us>)
Список pgsql-general
> On Wed, Jun 13, 2001 at 12:23:15PM +1000, Martijn van Oosterhout wrote:
> > select x from a where v in (select v from b)
> > select x from a where exists (select 1 from b where a.v = b.v)
>
> The latter should be faster than the former on every relational database
> system.

That surprises me because the subquery is a correlated subquery which
are usually slower on other databases that normal subqueries.

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