On Tue, Jun 30, 2009 at 01:14:10PM +0200, Waldemar Bergstreiser wrote: > I found a good explanation about informix outer joins. > > http://savage.net.au/SQL/outer-joins.html > > Please take a look at that. The syntax appears to make the expression of various idioms difficult; for example, how would I express the following: SELECT * FROM a LEFT JOIN b ON a.id = b.id WHERE b.id IS NULL OR a.c <> b.d; Admittedly I don't write code like this very often but, yes, I have used it on some occasions. I guess I'd have to resort to a subselect? I believe this is what Tom was referring to when he said that "there's no principled way to decide what it *means*". For example the semantics of the above are very different from either of: SELECT * FROM a LEFT JOIN b ON a.id = b.id OR a.c <> b.d WHERE b.id IS NULL; or: SELECT * FROM a LEFT JOIN b ON a.id = b.id AND (b.id IS NULL OR a.c <> b.d) and I can't think of any other formulations after reading the link you gave---it only seems to talk about binary operators involving columns from two tables. Second shouldn't be allowed, but I included it in case I was missing something. -- Sam http://samason.me.uk/ -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
