Question

Job
--------
Id
Description


JobStatus
----------
Id
JobId
StatusTypeId
Date

如何获取所有工作的当前JobStatus？

等等......

SELECT * FROM Job j
INNER JOIN ( /* Select rows with MAX(Date) grouped by JobId */ ) s
    ON j.Id = s.JobId

（我确信已经有很多类似的问题，但我找不到任何我需要的东西。）

Answer 1

在SQL Server 2005+：

SELECT  *
FROM    job j
OUTER APPLY
        (
        SELECT  TOP 1 *
        FROM    jobstatus js
        WHERE   js.jobid = j.jobid
        ORDER BY
                js.date DESC
        ) js

在SQL Server 2000：

SELECT  *
FROM    job j
LEFT JOIN
        jobstatus js
ON      js.id =
        (
        SELECT  TOP 1 id
        FROM    jobstatus jsi
        WHERE   jsi.jobid = j.jobid
        ORDER BY
                jsi.date DESC
        )

这些查询正确处理Date上的可能重复项。

Answer 2

一种方法是：

SELECT j.*, s2.StatusTypeId, s2.Date
FROM Job j
    JOIN
    (
        SELECT JobId, MAX(Date) AS LatestStatusDate
        FROM JobStatus 
        GROUP BY JobId
    ) s1 ON j.JobId = s1.JobId
    JOIN JobStatus s2 ON s1.JobId = s2.JobId AND s1.LatestStatusDate = s2.Date

假设您在JobStatus中没有2行用于相同的JobId +日期组合

Answer 3

SQL Server 2000的另一种（效率不高，但易于理解）解决方案： -

SELECT  *
FROM    job j
WHERE   j.date = (SELECT MAX(date) 
                  FROM   job 
                  WHERE  id = j.id)

加入到组中的MAX日期记录

3 个答案: