I think I have found a bug in version 7.1.3. (I have installed binary rpms from postgres site on rh7.1) Here is the DB and some sample entries. CREATE TABLE "timetest" ( "id" serial primary key, "timebegin" time, "timeend" time ); insert into timetest (timebegin,timeend) values ('12:00:20','12:01:00'); insert into timetest (timebegin,timeend) values ('14:00:20','14:02:00'); insert into timetest (timebegin,timeend) values ('15:00:00','15:00:40'); WORKS THIS SELECT DOESN'T WORK: select sum(timeend-timebegin) as totaltime from timetest; HERE IS WHAT POSTGRES REPORT: timetest=# select sum(timeend-timebegin) as totaltime from timetest; ERROR: Unable to select an aggregate function sum(time) timetest=# select version(); version ------------------------------------------------------------- PostgreSQL 7.1.3 on i686-pc-linux-gnu, compiled by GCC 2.96 (1 row) timetest=# ON POSTGRES 7.0.3 timetest=# select sum(timeend-timebegin) as totaltime from timetest; totaltime ----------- 00:03 (1 row) timetest=# select version(); version ------------------------------------------------------------- PostgreSQL 7.0.3 on i686-pc-linux-gnu, compiled by gcc 2.96 (1 row) ascor=# Hope this can help to fix the BUG! Alex ---------------------------(end of broadcast)--------------------------- TIP 6: Have you searched our list archives? http://www.postgresql.org/search.mpl