Jeff Davis <pgsql@xxxxxxxxxxx> writes: > 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). Just for the record, this is something that was added in SQL:99 --- our behavior conforms to the letter of earlier SQL versions. I think we have a TODO item to add at least some support for allowing implicit GROUP BY using functional dependencies, but it's kind of a worrisome thing. I don't know of any other part of the SQL spec whereby ALTER TABLE DROP CONSTRAINT could turn a formerly semantically legal query into an illegal query. Could have some unpleasant implications for the behavior of prepared statements. (Also, I'll bet a lot of money that mysql has not implemented this feature according to spec. The last I heard, as long as you have a GROUP BY they just blithely assume you know what you're doing and didn't write a query whose results are ambiguous.) 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
