Re: Slightly confused error message

Markus Schaber <schabi@logix-tt.com> writes:
> I just stumbled over a slightly confused error message:

> mydb=# select count(*),coverage_area from myschema.streets except select
> cd as coverage_area from countryref.disks group by streets.coverage_area;
> ERROR:  column "streets.coverage_area" must appear in the GROUP BY
> clause or be used in an aggregate function

> As the query looks, streets.coverage_area is actually used in the GROUP BY.

The complaint is 100% accurate; the subquery that it's unhappy about is
select count(*),coverage_area from myschema.streets

which is an aggregating query, but coverage_area is being used outside
an aggregate without having been grouped by.
        regards, tom lane