Re: where clauses and selects

From: Tim Landscheidt <tim(at)tim-landscheidt(dot)de>
To: pgsql-general(at)postgresql(dot)org
Subject: Re: where clauses and selects
Date: 2009-09-08 18:10:18
Message-ID: m3ab151f5h.fsf@passepartout.tim-landscheidt.de
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Scott Frankel <leknarf(at)pacbell(dot)net> wrote:

> Is it possible to perform a select in the where clause of a statement?

> I have a situation where I've got one arm tied behind my
> back: I can only have a single table in the select and from
> clauses, but the where clause appears to be freed from that
> restriction.

> Given a statement as follows:

> SELECT foo.foo_id, foo.name
> FROM foo, bar
> WHERE foo.bar_id = bar.bar_id
> AND bar.name = 'martini';

> I'm looking for a way to recast it so that the select and
> from clauses refer to a single table and the join
> referencing the second table occurs in the where clause.
> [...]

Something along the lines of:

| SELECT foo.foo_id, foo.name FROM foo WHERE foo.bar_id = (SELECT bar.bar_id FROM bar WHERE bar.name = 'martini');

should do the trick.

> I've explored the "where exists" clause, but it's not
> supported by the application toolkit I'm using. AFAIK, I've
> only got access to where ...

Dump it. Seriously. There are so many fine things you can do
with a full-fledged database - you certainly do not want to
be restricted in this regard.

Tim

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