> That's not a bug, it means what it says: HAVING clauses should contain
> aggregate functions. Otherwise they might as well be WHERE clauses.
> (In this example, flushing rows with negative a before the group step,
> rather than after, is obviously a win, not least because it would
> allow the use of an index on a.)
>
> However, I can't see anything in the SQL92 spec that requires you to
> use HAVING intelligently, so maybe this error should be downgraded to
> a notice? "HAVING with no aggregates would be faster as a WHERE"
> (but we'll do it anyway to satisfy pedants...)
If we allow them, then people can do things like:
HAVING max(a) > b
which seems strange. Would we handle that?
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