MS SQL选择具有条件的特定日期

Question

Ins No  AimSeqNumber    LearnRefNumber  LearnStartDate  DateEmpStatApp  EmpId
1000214  1                  10v1         2017-06-30     2016-08-30  900271388
1000214  1                  10v1         2017-06-30     2016-07-30  900271388
1000214  1                  10v1         2017-06-30     2014-07-30  900871388
1000214  1                  10v1         2017-06-30     2015-07-30  905271388

嗨，我有一张这样的桌子。我想在LearnStartDate上或之前获得最新DateEmpStatApp的empID

我不知道如何处理这个问题。我最初的逻辑是使用日期部分函数并找出天数的差异。然后使用min函数获取所选行。但是我仍然会得到不止一行。因为我只想要对应于learnstartdate

的最新DateEmpStatApp日期的empid

Answer 1

SELECT TOP (1) EmpId 
FROM MyTable
WHERE DateEmpStatApp < LearnStartDate
ORDER BY DateEmpStatApp DESC

只需限制符合条件的第一行

• ＆＃34;在LearnStartDate之前或之前的DateEmpStatApp＆＃34;
• ＆＃34;最新DateEmpStatApp＆＃34;

评论后编辑

SELECT EmpId, LatestDateEmpStatApp = MAX(DateEmpStatApp)
FROM MyTable
WHERE DateEmpStatApp < LearnStartDate
GROUP BY EmpId