SQL，基于变量的日期X和X之间的总和

Question

所以我在这个问题上挣扎了一下，我在基于小时的学校做入门级工作。

我需要找到所有已通过注册结束日期的学生，并从他们的第一次出勤日期到注册结束日期获得这些学生小时的总和。这是我写的代码的开始，但我知道我的Case是错误的。

示例学生A的出勤日期大于其合同结束日期。

在合同结束日期他的总小时数= 560

最小完成此计划为600小时

然后，我们添加一个附加费，以这40个小时，他已经没有结束日期完成。

我可以做数学，我只需要得到它，我可以在那里让学生身体。如果我添加诸如ATD.Attendancedate> = Reg.enddate之类的任何内容，它当然只会在结束日期之前拉动几小时。

SELECT CONCAT('<a href="admin_view_student.jsp?studentid=', 
    CAST(SDT.studentId AS CHAR), '">', CAST(SDT.firstName AS bCHAR), ' ', 
    CAST(SDT.lastName AS CHAR), '</a>') AS Name, 
    PGM.programmeName AS 'Program', 
    FORMAT(SUM(ATD.duration),2) AS 'Total Hours', 
    PGM.MinClockHours AS 'Program Total', 
    ATD.attendancedate AS 'ATTDATE', 
REG.Enddate AS 'EndDate', 
Case WHEN MAX(ATD.attendancedate) >= REG.Enddate Then Sum(ATD.duration) Between MIN(ATD.attendancedate) AND REG.enddate 
ELSE NULL END AS 'Whatever' 
FROM Attendance ATD 
INNER JOIN Registrations REG ON ATD.studentId = 
     REG.studentId AND REG.isActive = 1 
INNER JOIN Programmes  PGM ON REG.programmeId 
    = PGM.programmeId AND PGM.isActive = 1 
INNER JOIN Students   SDT ON REG.studentId = 
    SDT.studentId AND SDT.isactive = 1 
    WHERE 
    REG.ADMINID       AND 
    REG.enrollmentSemesterId = 4000441 AND 
    PGM.programmename Not like ('Careers Pathway') AND PGM.programmename Not like ('Instructor Training') AND 
    ATD.subjectId IN (SELECT GSR.subjectId 
      FROM CourseGroups CGP 
      INNER JOIN GroupSubjectReltn GSR ON CGP.courseGroupId=GSR.courseGroupId AND GSR.isActive=1 
      WHERE REG.programmeId = CGP.programmeId and CGP.isActive=1) 
             AND 
    ATD.classId IN (SELECT DISTINCT CRS.classId 
      From ClassStudentReltn CRS 
      Where CRS.studentId = ATD.studentId AND CRS.isActive=1) 
GROUP BY SDT.lastname 
ORDER BY SDT.firstName 

Answer 1

您可以通过自联接方式直接解决这个问题。您需要根据Where ATD.Attendancedate >= Reg.enddate选择有问题的学生，然后仅对满足该条件的学生进行计算。所以：

[your query] 
inner join 
    (SELECT studentId 
    FROM Attendance ATD 
    inner join Registrations REG 
    ON ATD.studentId = REG.studentId 
     AND REG.isActive = 1 
    WHERE ATD.Attendancedate >= Reg.enddate) as late 
on [your query].studentId = late.studentId