Aren Cambre <a...@arencambre.com> wrote: > SELECT COUNT(*) > FROM consistent.master > WHERE citation_id IS NOT NULL > UNION > SELECT COUNT(*) > FROM consistent.master > UNION > SELECT COUNT(*) > FROM consistent.master > WHERE citation_id IS NULL > > I got this result: > > 2085344 > 2085343 > 0 > > Not clear how adding a WHERE clause, whose only practical effect > is to reduce the number of rows returned, could cause *more* rows > to be returned. That seems buggy to me. Never assume that the rows will be returned in any particular order from a query unless you specify ORDER BY. Assuming, as you seem to be doing, that rows from the left side of a UNION will be output before rows from the right side is not safe. You have no way of knowing which row in a result set like that came from which of the UNIONed SELECTs. In this case your assumption is almost certainly wrong. -Kevin
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