Hi
Logically HAVING is executed after the GROUP BY and it must contain only the columns in the GROUP BY or aggregated function.
select state, count(state) as c from t group by state having c > 5
The above query grouped only on state and HAVING can be used only with the column state or the aggregated function count(state).
Regards,
R.Muralidharan
Rick Schumeyer <rschumeyer@ieee.org> wrote:
The following query returns an error (column c does not exist) in pg 8.0.3:
(The column state is the two letter abbreviation for a US state)
-- get the number of rows for each state; list in descending order; include only states with at least 6 rows
select state, count(state) as c from t group by state having c > 5 order by c desc; -- gives error
If I leave the having clause out, I get the expected results:
select state, count(state) as c from t group by state order by c desc; -- this works
Is this a bug or a feature? Im not sure why I can use c in the order by clause but not the having clause. pg is much happier with the full having count(state) > 5. Will this cause count to be evaluated twice?
If it matters, state is varchar(2).
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