On Sat, Jul 5, 2014 at 8:12 AM, Edson Richter <edsonrichter@xxxxxxxxxxx> wrote: > Thanks! > > I'll investigate (explain) performance for both versions. also be advised that in most cases when you use SQL 'UNION' you really should be using 'UNION ALL'. It's a very common mistake: UNION: form proper set union, combine set and remove tuple duplicates UNION ALL: append two sets For large sets, the duplicate removal can be expensive and possibly introduce subtle data dependent bugs in the worst case. merlin
