On Mon, 2009-05-04 at 12:30 -0500, Andy Colson wrote: > Yes, that query works in mysql, but only in mysql... and probably not in > any other db anywhere. It is not standard sql. My guess is that mysql > is "helping" you out by adding the customer.name for you... but maybe > not? Maybe its returning something else? Too bad it lets you write > confusing questions. Section 4.18 of SQL200n, "Functional Dependencies", shows some interesting ways that the DBMS can make the proper inferences (I think this is an optional feature, so I don't think PostgreSQL violates the standard here). I'm not sure if what DaNieL is asking for is actually covered by this feature, because it would need to infer the function dependencies: orders.id -> orders.code orders.id -> customer.name and the second one needs to be inferred through a couple steps, and that may be more sophisticated than what the standard asks for. It can be done though, because: orders.id -> orders.id_customer (implied by key on orders.id) orders.id_customer = customer.id (from join condition) customer.id -> customer.name (implied by key on customer.id) Therefore: orders.id -> customer.name So he's not asking for anything ridiculous, and it looks to me like he's supported by the standard (although I'm not an expert on the SQL standard). However, sometimes it's a good idea to be a little more explicit in the queries, just for the sake of readability. Regards, Jeff Davis -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
