postgres=# select except select;--(2 rows)postgres=# select intersect all select;--(2 rows)Why is it so?Should this be reported as a bug?.. ;)
The intersection case seems correct - one row from each sub-relation is returned since ALL is specified and both results as the same.
The except case looks like a bug because there should never be more rows returned from the combined query than the upper sub-query returns alone. Based upon the result of intersect it should in fact return zero rows - unless this one of those null-like scenarios where it is both equal and not equal at the same time...
David J.
