select distinct over specific columns

A query in a system I maintain returns

QID AID DATA
1   2   x
1   2   y
5   6   t

As per a new requirement, I do not want the (QID, AID)=(1,2) pair to be repeated. We also dont care what value is 开发者_运维问答selected from "data" column. either x or y will do.

What I have done is to enclose the original query like this

SELECT * FROM (<original query text>) Results group by QID,AID

Is there a better way to go about this? The original query uses multiple joins and unions and what not, So I would prefer not to touch it unless its absolutely necesary

If you don't care which DATA will be selected, GROUP BY is nice, though using ungrouped and unaggregated columns in SELECT clause of a GROUP BY statement is MySQL specific and not portable.