> From: Svein Erling Tysvær > Having said all that, I was somewhat surprised about one query I issued > yesterday: > > SELECT max(MyField) FROM TableA > UNION > SELECT max(MyField) FROM TableB > > used my descending indexes on MyField. However: > > SELECT 'TableA' as TableName, max(MyField) FROM TableA group by 1 > UNION > SELECT 'TableB', max(MyField) FROM TableB group by 1 > > used NATURAL for both tables ...
But it does not make much sense to use "UNION" instead of "UNION ALL" in this particular query :) Ivan
