我正在使用MS Access中的类调度数据库。有各种各样的课程，每一课都被教授多次，有时一天多次，但不一定每天都有。每门课程都有一套独特的软件和数据存储在笔记本电脑上。每个课程都有一套笔记本电脑，上面装有该软件。
对于任何特定的培训日，我需要为不同房间的正确班级分配一系列笔记本电脑ID，具体取决于该房间将有多少人参加该课程，以便教师知道要将哪些笔记本电脑带到那天他们和他们一起教课。
例如，我有原始数据：
Date Room ClassName HeadCount
---- ---- --------- ---------
11/30 101 Intro 10
11/30 102 Intro 15
11/30 103 Course 2 5
12/1 101 Intro 10
12/1 102 Course 2 15
12/1 103 Course 3 10
我也知道关于笔记本电脑的以下内容：
ClassName LaptopID
--------- ---------
Intro LT.Intro_1
Intro ...
Intro LT.Intro_30
Course 2 LT.Course 2_1
Course 2 ...
Course 2 LT.Course 2_30
Course 3 LT.Course 3_1
Course 3 ...
Course 3 LT.Course 3_30
基于以上两个表，我想输出：
Date Room ClassName HeadCount First Laptop Last Laptop
---- ---- --------- --------- ------------ -----------
11/30 101 Intro 10 LT.Intro_1 LT.Intro_10
11/30 102 Intro 15 LT.Intro_11 LT.Intro_25
11/30 103 Course 2 5 LT.Course 2_1 LT.Course 2_5
12/1 101 Intro 10 LT.Intro_1 LT.Intro_10
12/1 102 Course 2 15 LT.Course 2_1 LT.Course 2_15
12/1 103 Course 3 10 LT.Course 3_1 LT.Course 3_10
我知道这是一个窗口函数，但MS Access没有超前或滞后。有解决方法吗？
答案 0 :(得分：1)
您可能希望更改表定义以获得更好的性能。我已经重新提到了两张桌子。
您知道您的笔记本电脑ID是按顺序排列的，并且您知道每个班级的人数。为了跟随线索，您必须知道最后一个人数。 在当前的课程/活动之前，对于同一个班级的同一日期的参加者。
x = sum（headCount）其中id＆lt; currentID＆amp; classname = currentClassname＆amp; date = currentDate。 （当前表示currentRow。）
现在您知道当前行之前使用的笔记本电脑总数和当前行的headCount。第一台笔记本电脑将是
f = min(laptopid) where laptopid > x (x being totaLaptopUsedBefore this Row)
对于Last笔记本电脑，您还必须添加当前的人数。
l = min(laptopid) where laptopid >= currentHeadCount + x
注意f检查laptopid更大，L检查＆gt; =。
以下是一个可以改进的工作演示：
表1：tbl_ClassEvents
+----+------------+------+-----------+-----------+
| ID | date | Room | ClassName | HeadCount |
+----+------------+------+-----------+-----------+
| 1 | 30/11/2017 | 101 | Intro | 10 |
| 2 | 30/11/2017 | 102 | intro | 15 |
| 3 | 30/11/2017 | 103 | Course 2 | 5 |
| 4 | 01/12/2017 | 101 | Intro | 10 |
| 5 | 01/12/2017 | 102 | Course 2 | 15 |
| 6 | 01/12/2017 | 103 | Course 3 | 10 |
| 7 | 17/11/2017 | 101 | Intro | 16 |
+----+------------+------+-----------+-----------+
Table2: Tbl_ClassVsLaptop
+----+-----------+----------------+
| Id | ClassName | LaptopId |
+----+-----------+----------------+
| 1 | Intro | LT.Intro_1 |
| 2 | Intro | LT.Intro_2 |
| 3 | Intro | LT.Intro_3 |
| 4 | Intro | LT.Intro_4 |
| 5 | Intro | LT.Intro_5 |
| 6 | Intro | LT.Intro_6 |
| 7 | Intro | LT.Intro_7 |
| 8 | Intro | LT.Intro_8 |
| 9 | Intro | LT.Intro_9 |
| 10 | Intro | LT.Intro_10 |
| 11 | Intro | LT.Intro_11 |
| 12 | Intro | LT.Intro_12 |
| 13 | Intro | LT.Intro_13 |
| 14 | Intro | LT.Intro_14 |
| 15 | Intro | LT.Intro_15 |
| 16 | Intro | LT.Intro_16 |
| 17 | Intro | LT.Intro_17 |
| 18 | Intro | LT.Intro_18 |
| 19 | Intro | LT.Intro_19 |
| 20 | Intro | LT.Intro_20 |
| 21 | Intro | LT.Intro_21 |
| 22 | Intro | LT.Intro_22 |
| 23 | Intro | LT.Intro_23 |
| 24 | Intro | LT.Intro_24 |
| 25 | Intro | LT.Intro_25 |
| 26 | Intro | LT.Intro_26 |
| 27 | Intro | LT.Intro_27 |
| 28 | Intro | LT.Intro_28 |
| 29 | Intro | LT.Intro_29 |
| 30 | Intro | LT.Intro_30 |
| 31 | Course 2 | LT.Course 2_1 |
| 32 | Course 2 | LT.Course 2_2 |
| 33 | Course 2 | LT.Course 2_3 |
| 34 | Course 2 | LT.Course 2_4 |
| 35 | Course 2 | LT.Course 2_5 |
| 36 | Course 2 | LT.Course 2_6 |
| 37 | Course 2 | LT.Course 2_7 |
| 38 | Course 2 | LT.Course 2_8 |
| 39 | Course 2 | LT.Course 2_9 |
| 40 | Course 2 | LT.Course 2_10 |
| 41 | Course 2 | LT.Course 2_11 |
| 42 | Course 2 | LT.Course 2_12 |
| 43 | Course 2 | LT.Course 2_13 |
| 44 | Course 2 | LT.Course 2_14 |
| 45 | Course 2 | LT.Course 2_15 |
| 46 | Course 2 | LT.Course 2_16 |
| 47 | Course 2 | LT.Course 2_17 |
| 48 | Course 2 | LT.Course 2_18 |
| 49 | Course 2 | LT.Course 2_19 |
| 50 | Course 2 | LT.Course 2_20 |
| 51 | Course 2 | LT.Course 2_21 |
| 52 | Course 2 | LT.Course 2_22 |
| 53 | Course 2 | LT.Course 2_23 |
| 54 | Course 2 | LT.Course 2_24 |
| 55 | Course 2 | LT.Course 2_25 |
| 56 | Course 2 | LT.Course 2_26 |
| 57 | Course 2 | LT.Course 2_27 |
| 58 | Course 2 | LT.Course 2_28 |
| 59 | Course 2 | LT.Course 2_29 |
| 60 | Course 2 | LT.Course 2_30 |
| 61 | Course 3 | LT.Course 3_1 |
| 62 | Course 3 | LT.Course 3_2 |
| 63 | Course 3 | LT.Course 3_3 |
| 64 | Course 3 | LT.Course 3_4 |
| 65 | Course 3 | LT.Course 3_5 |
| 66 | Course 3 | LT.Course 3_6 |
| 67 | Course 3 | LT.Course 3_7 |
| 68 | Course 3 | LT.Course 3_8 |
| 69 | Course 3 | LT.Course 3_9 |
| 70 | Course 3 | LT.Course 3_10 |
| 71 | Course 3 | LT.Course 3_11 |
| 72 | Course 3 | LT.Course 3_12 |
| 73 | Course 3 | LT.Course 3_13 |
| 74 | Course 3 | LT.Course 3_14 |
| 75 | Course 3 | LT.Course 3_15 |
| 76 | Course 3 | LT.Course 3_16 |
| 77 | Course 3 | LT.Course 3_17 |
| 78 | Course 3 | LT.Course 3_18 |
| 79 | Course 3 | LT.Course 3_19 |
| 80 | Course 3 | LT.Course 3_20 |
| 81 | Course 3 | LT.Course 3_21 |
| 82 | Course 3 | LT.Course 3_22 |
| 83 | Course 3 | LT.Course 3_23 |
| 84 | Course 3 | LT.Course 3_24 |
| 85 | Course 3 | LT.Course 3_25 |
| 86 | Course 3 | LT.Course 3_26 |
| 87 | Course 3 | LT.Course 3_27 |
| 88 | Course 3 | LT.Course 3_28 |
| 89 | Course 3 | LT.Course 3_29 |
| 90 | Course 3 | LT.Course 3_30 |
+----+-----------+----------------+
以下是查询：
SELECT tbl_classEvents.ID
,tbl_classEvents.DATE
,tbl_classEvents.Room
,tbl_classEvents.ClassName
,tbl_classEvents.HeadCount
,(
SELECT min(laptopId)
FROM tbl_ClassVsLaptop T1
WHERE T1.ClassName = tbl_ClassEvents.ClassNAme
AND Mid([T1.LaptopID], InStrRev([T1.LaptopID], "_") + 1, 3) > (
+ Nz((
SELECT sum(headCount)
FROM tbl_classEvents T2
WHERE T2.ID < Tbl_ClassEvents.ID
AND T2.[DATE] = [Tbl_ClassEvents].[DATE]
AND T2.[ClassName] = [Tbl_ClassEvents].[ClassName]
), 0)
)
) AS FirstLaptop
,(
SELECT min(laptopId)
FROM tbl_ClassVsLaptop T1
WHERE T1.ClassName = tbl_ClassEvents.ClassNAme
AND Mid([T1.LaptopID], InStrRev([T1.LaptopID], "_") + 1, 3) >= (
+ [tbl_classEvents].[HeadCount] + Nz((
SELECT sum(headCount)
FROM tbl_classEvents T2
WHERE T2.ID < Tbl_ClassEvents.ID
AND T2.[DATE] = [Tbl_ClassEvents].[DATE]
AND T2.[ClassName] = [Tbl_ClassEvents].[ClassName]
), 0)
)
) AS LastLaptop
FROM tbl_classEvents
ORDER BY tbl_classEvents.DATE
,tbl_classEvents.Room
,tbl_classEvents.ClassNAme;
输出：
+----+------------+------+-----------+-----------+---------------+----------------+
| ID | DATE | Room | ClassName | HeadCount | FirstLaptop | LastLaptop |
+----+------------+------+-----------+-----------+---------------+----------------+
| 7 | 17/11/2017 | 101 | Intro | 16 | LT.Intro_1 | LT.Intro_16 |
| 1 | 30/11/2017 | 101 | Intro | 10 | LT.Intro_1 | LT.Intro_10 |
| 2 | 30/11/2017 | 102 | intro | 15 | LT.Intro_11 | LT.Intro_25 |
| 3 | 30/11/2017 | 103 | Course 2 | 5 | LT.Course 2_1 | LT.Course 2_5 |
| 4 | 01/12/2017 | 101 | Intro | 10 | LT.Intro_1 | LT.Intro_10 |
| 5 | 01/12/2017 | 102 | Course 2 | 15 | LT.Course 2_1 | LT.Course 2_15 |
| 6 | 01/12/2017 | 103 | Course 3 | 10 | LT.Course 3_1 | LT.Course 3_10 |
+----+------------+------+-----------+-----------+---------------+----------------+