Re: Find non-unique "key" values via SQL

On 1/9/07, Chris Payne <CPayne@xxxxxxxxxxxxxxx> wrote:

The reason for this is that the where conditions are applied before
aggregation and the having clause is applied after aggregation, so if
you wanted to use a sum() function and then drop all of the rows that
did not have a certain sum, you would have to use a having clause. I
assume that it has to come after the group by because it needs to count
up the rows before it can check the having clause, and it needs the
group by to know how to count up the rows.

That seems to make sense.  I was wondering how the SQL engine would
distinguish the pre- and post-aggregation when I had the count(*) test in
the WHERE clause.

Thanks,
Dan