Tarlika Elisabeth Schmitz wrote: > I have 2 tables T1 and T2 > > T1 has the columns: D, S, C. The combination of D,S,C is unique. > T2 has the columns: D, S, C, and boolean X. The combination of D,S,C is > not unique. > > I need to produce the following result for every occurrence of T1: > D,S,C, COUNT > > COUNT is the number of matching D,S,C combinations in T2 where X = true. > There might be no matching pair in T2 or there might be match but X > is false.
try something like: SELECT t1.d, t1.s, t1.c, count(*) FROM t1 LEFT JOIN ( SELECT d,s,c FROM t2 WHERE x ) AS t2_true USING (d,s,c) GROUP BY t1.d, t1.s, t1.c; Warning - not tested -- Richard Huxton Archonet Ltd -- Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-sql