SQL统计时间段内连续缺勤次数

Question

问题：我正在尝试计算每个学生在一周内某个特定班级的连续缺勤次数。

例如如果课程 MATH1234 在 Day 1 Period 4 和 Day 4 Period 3 有课程，而学生 0012345 缺席了 第 1 天第 4 期和第 4 天第 3 期 在第 1 周，就好像该学生缺席了 第 4 天第 3 期 em>第 1 周和第 1 天第 4 期第 2 周.

我有一个名为 Lessons 的表格，其中包含所有学生和他们注册的课程的运行列表，以及他们是否缺席任何课程：

课时([学号]、[班号]、[行号]、[学年]、[年]、[学期]、[周]、[日期间]、[ ClassDate], [IsAbsent], [ReasonCode], [ConsecutiveAbs])

我需要计算一个学生在一周内连续缺勤的每个班级的连续缺勤次数（见上面的解释）。

鉴于：

Student ID    Class Number    Line Number Academic Period Year    Term    Week    Day Period  ClassDate               IsAbsent    ReasonCode  ConsecutiveAbs
001234        1CVASX11        1           1               2011    1       3       1       2011-02-14 00:00:00.000     1           U           0
001234        1CVASX11        1           1               2011    1       4       1       2011-02-21 00:00:00.000     1           U           0
001234        1CVASX11        1           1               2011    1       4       2       2011-02-23 00:00:00.000     1           U           0
001234        1CVASX11        1           1               2011    1       5       1       2011-02-28 00:00:00.000     1           U           0
001234        1CVASX11        1           1               2011    1       5       2       2011-03-02 00:00:00.000     1           U           0
001234        1CVASX11        1           1               2011    1       6       1       2011-03-07 00:00:00.000     1           U           0
001234        1CVASX11        1           1               2011    1       6       2       2011-03-09 00:00:00.000     1           U           0
001234        1CVASX11        1           1               2011    1       7       2       2011-03-16 00:00:00.000     1           U           0
001234        1CVASX11        1           1               2011    1       9       1       2011-03-28 00:00:00.000     1           U           0
001234        1CVASX61        6           1               2011    1       9       2       2011-03-28 00:00:00.000     1           U           0

在 ClassDate 28/3 的班级编号 1CVASX11 的学生 001234 的连续 Abs 将为 1，因为该日期之前的缺勤是一周多前的 16/3。同样，ClassDate 9/3 上的 ConsecutiveAbs 将为 2，因为该学生也在一周内的 7/3 缺勤。

我目前正在做的是更新课程表，像这样改变 ConsecutiveAbs 的值：

UPDATE Lessons
SET ConsecutiveAbs = 
(SELECT ISNULL(SUM(CAST(IsAbsent AS numeric)), 0)
 FROM Lessons AS L3
 WHERE L3.IsAbsent = 1
 AND L1.IsAbsent <> 0
 AND L3.[Student ID] = L1.[Student ID]
 AND L3.[Class Number] = L1.[Class Number]
 AND L3.[Line Number] = L1.[Line Number]
 AND L3.[Year] = L1.[Year]
 AND L3.[ClassDate] <= L1.[ClassDate]
 AND (L3.[ClassDate] > (SELECT MAX(L2.ClassDate)
      FROM Lessons AS L2
      WHERE L2.IsAbsent = 0
      AND L2.[Student ID] = L1.[Student ID]
      AND L2.[Class Number] = L1.[Class Number]
      AND L2.[Line Number] = L1.[Line Number]
      AND L2.[Year] = L1.[Year]
      AND L2.ClassDate < L1.[ClassDate]
 ) OR (SELECT MAX(L2.ClassDate)
       FROM Lessons AS L2
       WHERE L2.IsAbsent = 0
       AND L2.[Student ID] = L1.[Student ID]
       AND L2.[Class Number] = L1.[Class Number]
       AND L2.[Line Number] = L1.[Line Number]
       AND L2.[Year] = L1.[Year]
       AND L2.ClassDate < L1.[ClassDate]
 ) IS NULL))
 FROM Lessons AS L1

但这给了我这个：

001234  1CVASX11    1   1   2011    1   3   1   2011-02-14 00:00:00.000 1   U   1
001234  1CVASX11    1   1   2011    1   4   1   2011-02-21 00:00:00.000 1   U   2
001234  1CVASX11    1   1   2011    1   4   2   2011-02-23 00:00:00.000 1   U   3
001234  1CVASX11    1   1   2011    1   5   1   2011-02-28 00:00:00.000 1   U   4
001234  1CVASX11    1   1   2011    1   5   2   2011-03-02 00:00:00.000 1   U   5
001234  1CVASX11    1   1   2011    1   6   1   2011-03-07 00:00:00.000 1   U   6
001234  1CVASX11    1   1   2011    1   6   2   2011-03-09 00:00:00.000 1   U   7
001234  1CVASX11    1   1   2011    1   7   2   2011-03-16 00:00:00.000 1   U   8
001234  1CVASX11    1   1   2011    1   9   1   2011-03-28 00:00:00.000 1   U   9
001234  1CVASX61    6   1   2011    1   9   2   2011-03-28 00:00:00.000 1   U   9

我需要在那里设置一个时间段，这样它只会在 ClassDate 的一周内加起来。有人知道吗？

Answer 1

我认为您缺少的一件是将计数限制为仅包括缺勤，即缺勤时间少于原始缺勤时间的 7 天。

以下查询包含该条件，我相信它会提供您正在寻找的结果：

UPDATE LessonsAbsent
SET ConsecutiveAbs = (
    SELECT 
        ISNULL(SUM(CAST(IsAbsent AS numeric)), 0)
    FROM 
        Lessons RunningTotalAbsent 
    WHERE
        RunningTotalAbsent.IsAbsent = 1
        AND LessonsAbsent.[Student ID] = RunningTotalAbsent.[Student ID]
        AND LessonsAbsent.[Class Number] = RunningTotalAbsent.[Class Number]
        AND LessonsAbsent.[Line Number] = RunningTotalAbsent.[Line Number]
        AND LessonsAbsent.[Year] = RunningTotalAbsent.[Year]
        AND LessonsAbsent.ClassDate >= RunningTotalAbsent.ClassDate

        -- Only count as consecutive if the absence happened within under 7 days.
        AND DATEDIFF(DAY, RunningTotalAbsent.ClassDate, LessonsAbsent.ClassDate) < 7
    )
FROM Lessons LessonsAbsent 
WHERE LessonsAbsent.IsAbsent = 1