来自两个不同表的生效日期，匹配特定日期的记录

Question

I am trying to pull employee records since 1/1/19. I am joining an employee history table to a job code detail table. For each employee record, I want to match the job code detail as of the effective date of the employee record. So if there was an employee record on 2/1/19, I would want the job code detail that was effective at the time; and for it not to pull in the top of stack job code detail which may have changed since 2/1/19. I am having issues with the proper coding.

I have tried the code below, but not sure it is correct. I joined the J2 table for another report I made to pull the top of stack job code record (ie WHERE J2.EFFDT = NULL). Not sure if something similar needs to be used for my current request, and how that is to be incorporated into the WHERE statement.

SELECT
    E.EMPLID AS [EE ID]
    ,E.Name AS [Name]
    ,E.EFFDT AS [Eff Date]
    ,E.COMPANY AS [Co.]
    ,E.JOBCODE AS [Job Code]
    ,E.JOBTITLE [Title]
    ,J.GRADE AS [MRR]
    ,J.BONUS AS [Bonus]
    ,J.OCC_TYPE AS [OCC]
    ,E.EMPL_STATUS_DESC AS [Status]
FROM Employee History AS [E]
LEFT JOIN JobCodeTable AS [J]
    ON E.JOBCODE = J.JOBCODE
LEFT JOIN JobCodeTable AS [J2]
    ON (
        J.JOBCODE = J2.JOBCODE 
        AND 
        J.EFFDT < J2.EFFDT
        )
WHERE E.EMPL_STATUS_DESC = 'Active'
    AND
    E.EFFDT >= '2019-01-01'
    AND
    E.EFFDT >= J.EFFDT

Sample results would be below. This is pulling all the employee records for Jane Doe and John Smith since 1/1/19. In this example each of their job codes had updates done in the job code detail table. Jane's MRR and Bonus attached to her job code were updated in the job code detail table effective 4/1/19. John's MRR and Bonus attached to his job code were updated in the job code detail table effective 2/10/19. When pulling the employee record, the results should pull the MRR and Bonus that were effective as of the listed date.

Employee History Table

EE ID   || Name       || Eff Date   || Co.   || Job Code || Title || Status    
12345   || Jane Doe   || 5/12/2019  || Apple || A9999    || VP    || Active    
12345   || Jane Doe   || 2/1/2019   || Apple || A9999    || VP    || Active    
54321   || John Smith || 6/5/2019   || Apple || A0002    || Mgr   || Active    
54321   || John Smith || 4/29/2019  || Apple || A0002    || Mgr   || Active    
54321   || John Smith || 1/12/2019  || Apple || A0002    || Mgr   || Active

Job Code Detail Table

Job Code|| Title || Eff Date    || MRR || Bonus || OCC 
A9999   || VP    || 4/1/2019    || 5   || 25%   || E     
A9999   || VP    || 1/12/2019   || 4   || 20%   || E    
A0002   || Mgr   || 2/10/2019   || 3   || 15%   || E       
A0002   || Mgr   || 11/01/2018  || 2   || 10%   || E    

What the report should pull

EE ID   || Name       || Eff Date   || Co.   || Job Code || Title || MRR|| Bonus || OCC || Status    
12345   || Jane Doe   || 5/12/2019  || Apple || A9999    || VP    || 5  || 25%   || E   || Active    
12345   || Jane Doe   || 2/1/2019   || Apple || A9999    || VP    || 4  || 20%   || E   || Active    
54321   || John Smith || 6/5/2019   || Apple || A0002    || Mgr   || 3  || 15%   || E   || Active    
54321   || John Smith || 4/29/2019  || Apple || A0002    || Mgr   || 3  || 15%   || E   || Active    
54321   || John Smith || 1/12/2019  || Apple || A0002    || Mgr   || 2  || 10%   || E   || Active

Answer 1

There may be more efficient ways, but I was able to figure it out using SELECT TOP within the SELECT statement.

SELECT E.EMPLID AS [EE ID]
    ,E.Name AS [Name]
    ,E.EFFDT AS [Eff Date]
    ,E.COMPANY AS [Co.]
    ,E.JOBCODE AS [Job Code]
    ,E.JOBTITLE [Title]
    ,(SELECT TOP 1 J.GRADE
        FROM JobCodeTable AS J
        WHERE E.JOBCODE = J.JOBCODE
        AND
        E.EFFDT >= J.EFFDT
        ORDER BY J.EFFDT DESC
    ) AS [MRR]
    ,(SELECT TOP 1 J.BONUS
        FROM JobCodeTable AS J
        WHERE E.JOBCODE = J.JOBCODE
        AND
        E.EFFDT >= J.EFFDT
        ORDER BY J.EFFDT DESC
    ) AS [Bonus]
    ,(SELECT TOP 1 J.OCC_TYPE
        FROM JobCodeTable AS J
        WHERE E.JOBCODE = J.JOBCODE
        AND
        E.EFFDT >= J.EFFDT
        ORDER BY J.EFFDT DESC
    ) AS [OCC]
    ,E.EMPL_STATUS_DESC AS [Status]
FROM Employee History AS [E]
WHERE E.EMPL_STATUS_DESC = 'Active'
    AND
    E.EFFDT >= '2019-01-01'