Re: Unions and Grouping

"Aaron Bono" <postgresql@aranya.com> writes:
> My question, what do the SQL Specifications say should happen on a Union?
> Is it supposed to eliminate duplicates even WITHIN the individual queries
> that are being unioned?

Yes.  SQL92 7.10 saith:
           b) If a set operator is specified, then the result of applying             the set operator is a table
containingthe following rows:
 
             i) Let R be a row that is a duplicate of some row in T1 or of                some row in T2 or both. Let m
bethe number of duplicates                of R in T1 and let n be the number of duplicates of R in                T2,
wherem >= 0 and n >= 0.
 
            ii) If ALL is not specified, then
                Case:
                1) If UNION is specified, then
                  Case:
                  A) If m > 0 or n > 0, then T contains exactly one dupli-                     cate of R.
                  B) Otherwise, T contains no duplicate of R.

        regards, tom lane