SQL Server - 在连接中删除派生查询

Question

我对以下示例感兴趣：如何1）摆脱左外连接中的派生查询; 2）删除/合并下面代码中的cte cteSecType连接中的派生查询选择最小值列表中的assistant_personnel_number;可以有多个与员工关联的主要和备用助理。 THX

WITH    cteAssistants ( executive_personnel_number, assistant_personnel_number, assistant_type, assign_role )
          AS ( SELECT   CASE WHEN ISNUMERIC(JP.XA_asgn_emplid) = 1
                             THEN JP.XA_asgn_emplid
                             ELSE ''
                        END AS executive_personnel_number ,
                        JAP.emplid AS assistant_personnel_number ,
                        LAT1.FIELDVALUE AS assistant_type ,
                        LAT3.xlatshortname AS assign_role
               FROM     dbo.XA_ASGN_PRNT AS KAP
                        LEFT OUTER JOIN dbo.XA_ASSIGNMENTS AS KA ON JP.emplid = JAP.emplid
                                                          AND JP.effdt = JAP.effdt
                        LEFT OUTER JOIN dbo.XA_EMPLOYEES AS EXECT ON EXECT.EMPLID = JP.XA_ASGN_EMPLID
                        LEFT OUTER JOIN dbo.XA_EMPLOYEES AS ASST ON ASST.EMPLID = JAP.EMPLID
                        LEFT OUTER JOIN dbo.XLATITEM AS XLAT1 ON LAT1.fieldname = 'XA_ASGN_TYPE'
                                                          AND LAT1.fieldvalue = JAP.XA_asgn_type
                        LEFT OUTER JOIN dbo.XLATITEM AS XLAT3 ON LAT3.fieldname = 'XA_ASGN_ROLE'
                                                          AND LAT3.fieldvalue = JP.XA_asgn_role
               WHERE    JAP.effdt = ( SELECT    MAX(effdt)
                                      FROM      dbo.XA_ASGN_PRNT
                                      WHERE     emplid = JAP.emplid
                                                AND effdt <= GETDATE()
                                    )
                        --Return data only when both executive and assistant are still active; null is for Floaters
                        AND ( EXECT.HR_STATUS = 'A'
                              OR EXECT.HR_STATUS IS NULL
                            )
                        AND ASST.HR_STATUS = 'A'

                        AND ( JAP.XA_asgn_type = 'F'

                              OR ( JAP.XA_asgn_type IN ( 'A', 'AF' )
                                   AND JP.XA_asgn_person = 'Y'
                                 )
                            )
             ),
        cteSecType ( assistant_personnel_number, SecType )
          AS ( SELECT   assistant_personnel_number ,
                        assistant_type AS SecType
               FROM     cteAssistants 
               GROUP BY assistant_type ,
                        assistant_personnel_number
             )
    SELECT  EMP.XA_NETWORK_ID AS network_id ,
            EMP.XA_EMPLID AS empid ,
            EMP.XA_EMPLID AS employeeNumber ,
            EMP.XA_FIRST_NAME AS first_name ,
            EMP.XA_LAST_NAME AS last_name ,
            SECRES.SecType AS SecType ,
            AsstInfo.XA_fml_pref_name AS PrimaryAssistant_FML ,
            AsstInfo.XA_network_id AS PrimaryAssistant_Newtork_ID ,
            AsstInfo.XA_EMPLID AS PrimaryAssistant_EmpID ,
            AsstInfo.XA_phone_ext AS PrimaryAssitant_Extension
    FROM    dbo.XA_EMPLOYEES AS EMP
            LEFT OUTER JOIN dbo.XA_EMPLOYEES AS MGR ON EMP.supervisor_id = MGR.emplid
            LEFT OUTER JOIN cteSecType AS SECRES ON CAST(CAST(SECRES.assistant_personnel_number AS INT) AS VARCHAR(11)) = EMP.XA_EMPLID
            LEFT OUTER JOIN ( SELECT    executive_personnel_number AS AttorneyID ,
                                        MIN(assistant_personnel_number) AS AssistantID
                              FROM      cteEmployeeAssistants AS A
                              WHERE     ( assign_role = 'Primary' )
                              GROUP BY  executive_personnel_number
                            ) AS ASST ON ASST.AttorneyID = EMP.XA_EMPLID
            LEFT OUTER JOIN dbo.XA_EMPLOYEES AS ASSTINFO ON ASSTINFO.XA_EMPLID = ASST.AssistantID
    WHERE   ( EMP.HR_STATUS = 'A' )
            AND ( EMP.PER_ORG IN ( 'EMP', 'CWR' ) )
            AND ( ISNULL(EMP.XA_NETWORK_ID, '') <> '' )   

GO