2012/3/30 Richard Huxton <dev@xxxxxxxxxxxx>: > On 30/03/12 08:46, Pavel Stehule wrote: >> >> 2012/3/30 Richard Huxton<dev@xxxxxxxxxxxx>: >>> >>> On 29/03/12 23:28, Pavel Stehule wrote: >>>> >>>> >>>> select anum from t1 where anum = 4 >>>> union all select 100 limit 1; >>> >>> >>> >>> I'm not sure the ordering here is guaranteed by the standard though, is >>> it? >>> You could end up with the 4 being discarded. >> >> >> A order is random for only "UNION", "UNION ALL" should to respect >> order. But I didn't check it in standard. > > > Let's put it this way - a quick bit of googling can't find anything that > says the order *is* guaranteed, and (almost?) no other operations do so by > default. > yes, it should to work in pg, but it should not work else where. secure solution is SELECT x FROM (SELECT * FROM (SELECT 1, x FROM tab WHERE x = 10 LIMIT 1) s1 UNION ALL SELECT 2, -1000 ORDER BY 1 LIMIT 1) s2; Regards Pavel Stehule > > -- > Richard Huxton > Archonet Ltd -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
