Re: Check for an empty result

Hi Andreas!

--- On Fri, 2/13/09, A. Kretschmer <andreas(dot)kretschmer(at)schollglas(dot)com> wrote:

> In response to Eus :
> > Hi Ho!
> >
> > Is there a way to check whether or not a subquery
> returns an empty result set?
>
> You can use EXISTS for that:
>
> -- empty result
> test=*# select * from (select 1 where 1=2) foo;
> ?column?
> ----------
> (0 rows)

That's good that it can be used in FROM phrase too besides WHERE phrase.

> -- check if a result exists
> test=*# select exists(select * from (select 1 where 1=2)
> foo);
> ?column?
> ----------
> f
> (1 row)
>
> test=*# select exists(select * from (select 1 where 1=1)
> foo);
> ?column?
> ----------
> t
> (1 row)

Even in SELECT phrase? That's great!

Thank you for the information.

> Regards, Andreas
> --
> Andreas Kretschmer
> Kontakt: Heynitz: 035242/47150, D1: 0160/7141639 (mehr:
> -> Header)
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Best regards,
Eus (FSF member #4445)

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