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Re: [HACKERS] Re: subselects

From: The Hermit Hacker <scrappy(at)hub(dot)org>
To: Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us>
Cc: Zeugswetter Andreas DBT <Andreas(dot)Zeugswetter(at)telecom(dot)at>, pgsql-hackers(at)hub(dot)org
Subject: Re: [HACKERS] Re: subselects
Date: 1998-01-21 15:18:29
Message-ID: Pine.NEB.3.95.980121101747.14635T-100000@hub.org (view raw or flat)
Thread:
Lists: pgsql-hackers
On Wed, 21 Jan 1998, Bruce Momjian wrote:

> > 
> > Bruce wrote:
> > > I have completed adding Var.varlevelsup, and have added code to the
> > > parser to properly set the field.  It will allow correlated references
> > > in the WHERE clause, but not in the target list.
> > 
> > select i2.ip1, i1.ip4 from nameip i1 where ip1 = (select ip1 from nameip
> > i2);
> >    522: Table (i2) not selected in query.
> > select i1.ip4 from nameip i1 where ip1 = (select i1.ip1 from nameip i2);
> >    284: A subquery has returned not exactly one row.
> > select i1.ip4 from nameip i1 where ip1 = (select i1.ip1 from nameip i2
> > where name='zeus');
> >  2 row(s) retrieved.
> > 
> > Informix allows correlated references in the target list. It also allows
> > subselects in the target list as in:
> > select i1.ip4, (select i1.ip1 from nameip i2) from nameip i1;
> >    284: A subquery has returned not exactly one row.
> > select i1.ip4, (select i1.ip1 from nameip i2 where name='zeus') from
> > nameip i1;
> >  2 row(s) retrieved.
> > 
> > Is this what you were looking for ?
> > 
> > Andreas
> > 
> > 
> 
> Yes, I know other engines support subqueries and references in the
> target list.  I want to know if we are going to do that for 6.3. 
> Personally, I have never seen much use for it.

	If its easy to add in the next couple of days, sure, go for
it...but can someone explain to me *why* you would use a subselect in the
target list?  I've actually never seen that before :9



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