>>

>>;with cte as (SELECT q.GroupId, 
>>       (SumOfcert_complete/CountOfcert_complete)*100 AS Percent_Certified, 
>>       Groups.GroupName    FROM qryGroupCert_base AS q 
>>    INNER JOIN Groups ON q.GroupId=Groups.GroupId)
>>
>>select * from cte
>>UNION ALL
>>select 0 as GroupID, SUM(Percent_Certified), 'ALL' as GroupName
>>from cte

>
>Why CTE?

Why not - seems like a simple way. Of course, if we would have GROUP BY, we can easily add CUBE or ROLLUP statement instead.