左连接中的Where子句使用相关查询？

Question

这是查询:

SELECT c.Name As CompanyName, j.ID as JobID, j.Title as JobTitle, 
ja.ApplicationDate, DATEDIFF(MONTH,ja.ApplicationDate, GETDATE()) AS MonthsAgo,
jsc.Name As Recruiter, js.Name As RecruitingAgency, jsh.Name As LastStatus
FROM Companies c
JOIN Jobs j 
ON c.ID = j.CompanyID
JOIN JobApplications ja
ON j.ID = ja.JobID
LEFT JOIN JobContact jsc
ON jsc.ID = j.JobSourceContactID
LEFT JOIN JobContactCompany js
ON jsc.JobSourceCompanyID = js.ID
LEFT JOIN (
    SELECT TOP 1 jh.JobID, jh.StatusDate, jt.Name
    FROM JobStatusHistory jh
    JOIN JobStatusTypes jt
    ON jh.JobStatusTypeID = jt.ID
    --WHERE jh.JobID = j.ID
    ORDER BY jh.StatusDate DESC
    ) jsh
ON j.ID = jsh.JobID
ORDER BY ja.ApplicationDate

我正在努力获得特定工作的最新工作状态.我无法弄清楚如何在LEFT JOIN中执行where子句(注释的WHERE).我过去做过这个,但不记得我过去是怎么做到的.

我会感激任何指针.

Answer 1

您需要使用OUTER APPLY.CROSS Apply类似于INNER JOIN,其中应用的表必须返回结果,而OUTER Apply类似于[LEFT] OUTER JOIN,其中应用的子查询可能不返回任何结果.

SELECT c.Name As CompanyName, j.ID as JobID, j.Title as JobTitle, 
    ja.ApplicationDate, DATEDIFF(MONTH,ja.ApplicationDate, GETDATE()) AS MonthsAgo,
    jsc.Name As Recruiter, js.Name As RecruitingAgency, jsh.Name As LastStatus
FROM Companies c
JOIN Jobs j ON c.ID = j.CompanyID
JOIN JobApplications ja ON j.ID = ja.JobID
LEFT JOIN JobContact jsc ON jsc.ID = j.JobSourceContactID
LEFT JOIN JobContactCompany js ON jsc.JobSourceCompanyID = js.ID
OUTER APPLY ( 
    SELECT TOP 1 jh.JobID, jh.StatusDate, jt.Name
    FROM JobStatusHistory jh
    JOIN JobStatusTypes jt
    ON jh.JobStatusTypeID = jt.ID
    WHERE jh.JobID = j.ID
    ORDER BY jh.StatusDate DESC
    ) jsh
ORDER BY ja.ApplicationDate