On 2010-11-24, Daniel Verite <daniel@xxxxxxxxxxxxxxxx> wrote: > Fredric Fredricson wrote: > >> But if you change the column names in the second SELECT in the UNION this is >> ignored: >> # SELECT c1,c2 FROM (SELECT 1 AS c1, 2 AS c2 UNION SELECT 2 AS c3, 1 AS c4) >> AS x; >> c1 | c2 >> ----+---- >> 1 | 2 >> 2 | 1 >> Apparently, in a UNION the column names are derived from the first statement >> only. > > The example upthread demonstrates that in certain contexts, column positions > are relevant whereas column names are not. The modified query you show here > doesn't lead to any different conclusion. > > The allegation that row.* doesn't come with a deterministic column order > remains pretty much unsubstantiated at this point. It's deterministic, just subject to change (eg if the table is re-created with a different order, or if a column is dropped and re-added) I try to always use column and table names when dealing with tables other people could mess with. If dealing with a temp table I sometimes take shortcuts as the source is all in one place, so anyone messing with it will hopefully be aware of the consequences of their actions. -- ââ 100% natural -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
