Merlin Moncure <mmoncure@xxxxxxxxx> writes: > On Mon, May 18, 2009 at 3:13 PM, Joshua Berry <yoberi@xxxxxxxxx> wrote: >> Is there an easy and efficient way to return a boolean false for a query >> that returns no result, and true for one that does return a result? > Probably the best general approach is to: > select count(*) = 1 from > ( > <query> limit 1 > )q; Seems like EXISTS() is much more straightforward ... > the point being that in some cases (not all obviously) the limit 1 can > be a huge win, as you only care if there are rows or not. ... the system does know about optimizing EXISTS as if it were a LIMIT query; you don't need to tack that on yourself. regards, tom lane -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
