Hvordan reducerer man mange lignende korrelerede underforespørgsler?

SELECT j.EmployeeId
       ,j.CompanyId
       ,j.JobCode
       ,COALESCE(j.CustomWageRate, r.WageRate, ca.WageRate, 0) AS EffectiveRate
       ,COALESCE(r.CustomBurdenRateReg, ca.CustomBurdenRateReg) AS CustomBurdenRateReg
       ,COALESCE(r.CustomBurdenRateOvt, ca.CustomBurdenRateOvt) AS CustomBurdenRateOvt
       ,COALESCE(r.CustomBurdenRateDbl, ca.CustomBurdenRateDbl) AS CustomBurdenRateDbl
       ,j.EffectiveDate
FROM   ContractLabor.EmployeeJobDetails j
       LEFT JOIN ContractLabor.CompanyJobRates r
         ON j.CompanyId = r.CompanyId
            AND j.JobCode = r.JobCode
            AND j.EffectiveDate = r.EffectiveDate

       OUTER APPLY --or CROSS APPLY
       (
            SELECT TOP 1 WageRate
                    ,CustomBurdenRateReg
                    ,CustomBurdenRateOvt
                    ,CustomBurdenRateDbl
            FROM   ContractLabor.CompanyJobRates
            WHERE  CompanyId = j.CompanyId
                    AND JobCode = j.JobCode
                    AND EffectiveDate < j.EffectiveDate
            ORDER  BY EffectiveDate DESC       
       ) ca