>>> On Tue, Dec 19, 2006 at 9:58 AM, in message <[EMAIL PROTECTED]>, Tom Lane <[EMAIL PROTECTED]> wrote: > "Kevin Grittner" <[EMAIL PROTECTED]> writes: >> I'm having trouble seeing how it is a useful construct in the context >> of a scalar subquery. A non- standard extension should be useful in some >> way. > > There is 0 chance that we'd disallow it at the top level after allowing > it all these years. I wouldn't want to eliminate it there -- it is clearly a useful extension to the standard at the top level. > And probably not even just top- level; consider > select 1 union all select 2 union all select 3; > which has been the recommended workaround up to 8.2 for our lack of > multi- row VALUES lists. We will certainly break a lot of code if we > disallow that. Point taken. > So now you have to make a case why we should make a > non- orthogonal distinction between certain subqueries and other > subqueries. Well, I don't think of the terms for set operations as subqueries, and there are other differences already in what is allowed for a query term and a subquery. Arguably there is more risk of error of the type recently reported where you are in a scalar subquery context. > As for potential usefulness, consider a set- returning function invoked > in the targetlist: it makes perfect sense to do > WHERE foo IN (SELECT mysrf(...)) > and maybe even add an ORDER BY/LIMIT to that. That is sufficient to answer my concerns. I tend to operate from the context of the standard, because we have our own ANSI based parser which generates portable Java query classes. ORDER BY and LIMIT are not allowed in the subqueries in the standard but are obviously useful extensions. The missing FROM then adds value to the other extensions. Case closed. Thanks. By the way, when I read my previous message it struck me that it could be taken with a tone I didn't intend. That was the result of whipping it out quickly without taking sufficient time to review it. Sorry; no offense was intended. I'll try to avoid doing that again. -Kevin
---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend