具有多个表的SQL查询，可以仅通过count（*）来应用group？

I am trying to list bookjobs info for jobtype 'N' and having publishers creditcode of 'C'. Then, add a count of the total number of po's (purchase orders- from table pos) for each row of the previous queries' output. Can you use group by to apply only to that count and not to the rest of the query? Do i have to use a join? My attempts thus far have been unsuccessful. These are the tables i am working with:I am trying to list bookjobs info for jobtype '