SQL Server - get rid of derived query in join - sql

Question

I'm interested in some suggestions with examples on how to 1)get rid of the derived query in the left outer join and 2)remove/consolidate the cte cteSecType in the code below The derived query in the join chooses the minimum assistant_personnel_number out of a list; there can be multiple primary and backup assistants associated with an employee . 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