An IN subquery must return only one field

select TABLE1.* FROM TABLE1 WHERE ID_FLD IN (
  select TABLE2.ID_FLD FROM TABLE2 WHERE ...) 

>
>I am getting error "invalid subquery" when using the following SQL Select:
>
>

>select TABLE1.* FROM TABLE1 WHERE ID_FLD IN (select TABLE2.ID_FLD, SUM(
> TABLE2.QUANTITY)  as USED_QUANTITY FROM TABLE2 GROUP BY TABLE2.ID_FLD) 
>

>
>The only thing that I see that could be causing this error is GROUP BY. Is this correct?