Join two tables and filter

 SELECT * FROM (

SELECT ArchiveAppraisalID, OriginalAppraisalID, AppraisalType, EmpNumber, (A.FIRST_NAME + ',' + A.LAST_NAME) AS EmpName FROM Reports.Appraisals B JOIN tbl_HRITMasterData A ON A.EMPLOYEE_NUMBER = B.EmpNumber UNION ALL SELECT B.ArchiveMidYear AS ArchiveAppraisalID, B.OriginalMidYearID As OriginalAppraisalID, B.AppraisalType, B.EmpNumber, (A.FIRST_NAME + ',' + A.LAST_NAME) AS EmpName FROM Reports.MidYear B JOIN tbl_HRITMasterData A ON A.EMPLOYEE_NUMBER = B.EmpNumber ) AS CombinedData WHERE (@SearchName IS NULL OR (EmpName LIKE '%' + @SearchName + '%'));