WITH FirstClient (Last,first,rep,qtr,rn) as
    (
     select 
        LastName as Last,
        FirstName as First,
        SalesRep as Rep,
        Quarter as Qtr,
        ROW_NUMBER OVER (PARTITION by LastName,FirstName ORDER by 
                                     LastName,FirstName,Quarter,SalesRep) as rn
     from MyClientTable
    )
select 
        last,
        first,
        rep,
        qtr
from FirstClient
where rn=1