On Wed, October 19, 2011 15:01, Kerem Kat wrote: > Adding CORRESPONDING to Set Operations > Initial patch, filename: corresponding_clause_v2.patch
I had a quick look at the behaviour of this patch. Btw, the examples in your email were typoed (one select is missing): > SELECT 1 a, 2 b, 3 c UNION CORRESPONDING 4 b, 5 d, 6 c, 7 f; should be: SELECT 1 a, 2 b, 3 c UNION CORRESPONDING select 4 b, 5 d, 6 c, 7 f; and > SELECT 1 a, 2 b, 3 c UNION CORRESPONDING BY(b) 4 b, 5 d, 6 c, 7 f; should be: SELECT 1 a, 2 b, 3 c UNION CORRESPONDING BY(b) select 4 b, 5 d, 6 c, 7 f; > But there is also a small bug, I think: the order in the CORRESPONDING BY list should be followed, according to the standard (foundation, p. 408): "2) If <corresponding column list> is specified, then let SL be a <select list> of those <column name>s explicitly appearing in the <corresponding column list> in the order that these <column name>s appear in the <corresponding column list>. Every <column name> in the <corresponding column list> shall be a <column name> of both T1 and T2." That would make this wrong, I think: SELECT 1 a, 2 b, 3 c UNION CORRESPONDING BY(c,b) select 5 d, 6 c, 7 f, 4 b ; b | c ---+--- 2 | 3 4 | 6 (2 rows) i.e., I think it should show columns in the order c, b (and not b, c); the order of the CORRESPONDING BY phrase. (but maybe I'm misreading the text of the standard; I find it often difficult to follow) Thanks, Erik Rijkers -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
