"Mason Hale" <masonhale@gmail.com> writes:
> The query below should return 10 rows,
Not by my reading of the spec. SQL92 7.10 saith:
b) If a set operator is specified, then the result of applying
the set operator is a table containing the 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 be the number of duplicates
of R in T1 and let n be the number of duplicates of R in
T2, where m >= 0 and n >= 0.
...
iii) If ALL is specified, then
...
3) If INTERSECT is specified, then the number of duplicates
of R that T contains is the minimum of m and n.
You have m = 1, n = 2 for each distinct row at the INTERSECT step,
ergo you get one copy out.
regards, tom lane