Question: What are the average work experiences of the users professionally using each of the operating systems?
SQL:
select os.name, avg(r.WorkExp) as WorkExp  from responses r join Response_OpSysProfessionalUse as res on r.id=res.response_id join OperatingSystems as os on res.OperatingSystems_id=os.id where r.WorkExp is not Null group by os.name order by WorkExp desc