Non-group columns with aggregate functions

Hi All,

I had seen the answer for my question before, but hacker's E-mail search
isn't finding any word.

I'm using PgSQL 6.5.2 with RHLinux 6.0.

How can I use non-group columns in a select with aggregate functions ? To
me, the following query makes sense.

teste=> create table people(pp_id int2 primary key, pp_name text);
NOTICE: CREATE TABLE/PRIMARY KEY will create implicit index 'people_pkey'
for table 'people'
CREATE
teste=> create table workpgsql(wp_people int2, wp_date date, hoursofwork
int2);
CREATE
teste=> insert into people values (1,'ME');
INSERT 226808 1
teste=> insert into people values (2,'YOU');
INSERT 226809 1
teste=> insert into workpgsql values (1,'01/01/2000',5);
INSERT 226810 1
teste=> insert into workpgsql values (1,'01/01/2000',4);
INSERT 226811 1
teste=> insert into workpgsql values (2,'01/01/2000',6);
INSERT 226812 1
teste=> insert into workpgsql values (2,'01/01/2000',6);
INSERT 226813 1
teste=> select pp_name,wp_date,sum(hoursofwork) from people,workpgsql
teste-> where pp_id=wp_people
teste-> group by wp_people,wp_date;
ERROR: Illegal use of aggregates or non-group column in target list

If anybody knows how to rebuild this query to work, thanks in advance.

Thanks,

Ricardo Coelho.