sql query bug???

Is this a bug (in 9.0.4), or have I just gone cross-eyed from too much work?

The query:

select t0."ICD9", t0."Description", count(*)
from (select distinct "Person_Id", "ICD9", "Description" from "PatientDiagnoses") as t0
group by (t0."ICD9", t0."Description")
order by count(*) desc limit 10;

The error:

column "t0.ICD9" must appear in the GROUP BY clause or be used in an aggregate function

Huh?

FWIW, I'm not providing the "PatientDiagnoses" def because it's a complex query involving 3-way union of 5-way joins--intended for end-user querying.

Of note, this query works (and performance is good enough as well):

select "ICD9", count(*) from (select distinct "Person_Id", "ICD9" from "PatientDiagnoses") as t0 group by "ICD9" order by count(*) desc limit 10;

--
Scott Ribe
scott_ribe(at)elevated-dev(dot)com
http://www.elevated-dev.com/
(303) 722-0567 voice