On Sun, 9 May 1999, Thomas Lockhart wrote:
> > > Am I right in thinking that UNION (without ALL) is defined to do a
> > > DISTINCT on its result, so that duplicates are removed even if the
> > > duplicates both came from the same source table? That's what 6.4.2
> > > does, but I do not know if it's strictly kosher according to the SQL
> > > spec.
>
> Yes, this is the right behavior according to SQL92...
In which case something should put a DISTINCT on queries using UNION...
since making T_Query nodes never equal is a deoptimization.
Taral