SQL

As a follow up to the questions I had the other day, I've ordered the 
appropriate license key for the SQL and have started working on learning 
embedded sql to use with my rpg.

Needless to say, it'll delay some reports a bit but I think in the long run 
it'll help.

One question I do have, I am running the sql interactive query and I am just 
playing with it a bit, but have run into a problem that maybe one of you can 
help me out with; considering the slightly different syntax between sql for 
the iSeries and what I am used to.

I have a PF that cotnains among other fields, ilneprice (which contains 
extended price amount), and a ilnsoldto field which is a reference field for 
the customer number.

When I run 'select ilnsoldto' by itself it runs fine, when I run sum
(ilneprice) by itself its fine but when I run the following command it tells 
me the ilnsoldto field is incorrect:

select ilnsoldto, sum(ilneprice) from impiln00

Suggestions? Comments?