I have a problem with a very simple query

select sum(sub_weight) weighttotal
from order_details
where order_id = :Aorder_id

when I put this query in sql+ it works with no problems it returns the total weight for the order_id I specify....

However when I put this query in an ADOQuery it gives me a
ORA 00937 not a single-group group function

Does Delphi have a different way to see this simple query? all I need to do is get the total weight from an order_id to calculate the shipping cost from a webservice....

Can anyone give me some tips? or suggestions?
** new to delphi **