Union Functionality works for instructor Assigned courses

I was trying aggregation but end up making UNION query.

select * from
(select * from
 (select iID, count(iID) from
courseassignment
        group by iID) m
where iID=8) x

union

(select iID, sum(Credits) from
    (select * from
courseassignment
  where iID=8) a
 natural join course c)