[SQL] GROUP by

[Antti Linno]

I have table job, and I want to select data from it, grouping by
workgroups. When I use 
 select id,name from job where workgroup='top leaders' AND ...  group by
workgroup;
When I want to group, I get 
ERROR:  Illegal use of aggregates or non-group column in target list
I'm confused, why does query work only with sum,min etc. alone in
select.

Antti