...AS FlatRate_FeeSchedule, t2.fingroup,t2.effectivedate, t1.perdiem_rate,t4.flatratediscount,t4.fingroup, t4.effectivedate
FROM
(SELECT a1.*
FROM dbo_SLAR_Client AS a1
LEFT JOIN
(SELECT COMPANYID,MASTER_CLIENTID
FROM dbo_SLAR_Client
GROUP BY COMPANYID,MASTER_CLIENTID ) AS a2
ON...