我正在尝试制作一个公式，让学生的奖励积分与他们的消极行为标志相对应。
学生获得LEAP积分（在transactions表中）以获得积极的行为。他们根据奖励的类别获得更多积分，即Model Citizen给予学生10分。
另一方面，学生会因为负面行为而获得单一旗帜。然后在数据库表中对Flag的类别进行加权，即Aggressive Defiance类别的权重高4，而Low Level Disruption只有值 { {1}}。
因此，困难在于试图考虑旗帜类别的权重。它们存储在1列下的categories表中。
以下是SQL小提琴：http://sqlfiddle.com/#!2/2e5756
在我看来，伪SQL代码看起来像这样......
Weight然而，我不知道如何在MySQL中实现SELECT
CONCAT( stu.Surname, ", ", stu.Firstname ) AS `Student`,
SUM(t.Points) AS `LEAP Points`,
SUM(<<formula>>) AS `Flags`
( `LEAP Points` - `Flags` ) AS `Worked Out Points Thing`
FROM student stu
LEFT JOIN transactions t ON t.Recipient_ID = stu.id
LEFT JOIN flags f ON f.Student_ID = stu.id
LEFT JOIN categories c ON f.Category_ID = c.ID
GROUP BY stu.id
。它必须是这样的：
<<formula>>所以，如果学生有这些旗帜......
SUM OF[ Each of Student's Flags * that Flag's Category Weighting ]
他们在#1 f.Reason "Being naughty", f.Category_ID "1", c.Title "Low Level Disruption", c.Weight "1"
#1 Reason "Aggressively naughty!", Category "Aggressive Defiance", Category Weighting "4"
#1 Reason "Missed detention", Category "Missed Detention", Category Weighting "3"
等式中总共需要1+4+3 = 9个点。
因此，所需的输出基本上是......
Worked Out Points Thing从上面的SQL小提琴，这里是必需的输出..我错过了一些学生，因为我必须手动解决这些问题：
Student LEAP Points Flags Equation Points LEAP Points minus Flag Points
D Wraight 1000 800 200
D Wraight2 500 800 -300
D Wraight3 1200 300 900
这将有助于我们在查看年终奖励旅行时，为每位学生提供选择。
希望这是有道理的...有点难以解释它...
提前致谢，
答案 0 :(得分：1)
找出你的公式＆＃39;首先是因为它是最深的部分。向外工作。 建立一个标志*每个学生的重量表
select sum(weight), student_id from flags f
join categories c
on f.category_id = c.id
group by student_id
所以现在你已经从每个学生的交易总数中得到一个标志值表减去
select sum(points), recipient_id from transactions
group by recipient_id
所以现在我们有两个表，其中包含学生ID的正值和负值（显然假设学生ID是收件人ID） 你希望那些有事务但没有标志的人出现在结果中，所以外连接。 并且数字减去null为null所以如果ifnull函数在标志上得到0
select a.student, points - ifnull(penalties, 0) as netPoints
from
(select sum(points) as points, recipient_id as student from transactions
group by student) as a
left outer join
(select sum(weight) as penalties, student_id as student from flags f
join categories c
on f.category_id = c.id
group by student) as b
on
a.student = b.student
所以在那里的名字只是
select
concat(firstname, ', ', surname) as name,
ifnull(points,0) as totalPoints,
ifnull(penalties,0) as totalPenalties,
ifnull(points,0) - ifnull(penalties, 0) as netPoints,
ifnull(countFlags, 0)
from
student
left join
(select sum(points) as points, recipient_id as student from transactions
group by student) as a
on student.id = a.student
left join
(select sum(weight) as penalties, count(f.id) as countFlags, student_id as student from flags f
join categories c
on f.category_id = c.id
group by student) as b
on
student.id = b.student
加入条件始终来自学生的id列，它永远不会为空。 可能有更有效的方式，但是谁在乎呢？
答案 1 :(得分：0)
回到问题（冒着重复自己的风险！），给定以下数据集，期望的结果集会是什么样的......
SELECT * FROM flags;
+------+------------+----------+---------------------+-----------+-------------+--------------------------+---------------------+
| ID | Student_ID | Staff_ID | Datetime | Period_ID | Category_ID | Action_Taken_Category_ID | Action_Taken_Status |
+------+------------+----------+---------------------+-----------+-------------+--------------------------+---------------------+
| 8843 | 137608 | 35003 | 2014-03-11 08:31:00 | 8 | 16 | 7 | P |
| 8844 | 137608 | 35003 | 2014-03-11 08:31:00 | 8 | 16 | 7 | P |
| 8845 | 139027 | 35003 | 2014-03-11 08:31:00 | 8 | 16 | 7 | P |
| 8846 | 139041 | 35003 | 2014-03-11 08:31:00 | 8 | 16 | 7 | P |
| 8847 | 139041 | 34961 | 2014-03-11 09:01:02 | 2 | 12 | 26 | P |
| 8848 | 139041 | 34996 | 2014-03-11 09:23:21 | 3 | 12 | 27 | C |
| 8849 | 139041 | 35022 | 2014-03-11 11:07:46 | 4 | 34 | 28 | P |
| 8850 | 139892 | 138439 | 2014-03-11 11:12:47 | 4 | 21 | 7 | C |
| 8851 | 138832 | 138439 | 2014-03-11 11:12:48 | 4 | 21 | 7 | C |
| 8852 | 34533 | 138439 | 2014-03-11 11:12:48 | 4 | 21 | 7 | C |
+------+------------+----------+---------------------+-----------+-------------+--------------------------+---------------------+
SELECT * FROM categories;
+----+------+--------------------------------------+--------+----------+
| ID | Type | Title | Weight | Added_By |
+----+------+--------------------------------------+--------+----------+
| 10 | F | Low level disruption | 1 | NULL |
| 11 | F | Swearing directly at another student | 2 | NULL |
| 12 | F | Late | 1 | NULL |
| 13 | F | Absconded | 3 | NULL |
| 14 | F | Refusal to follow instruction | 3 | NULL |
| 15 | F | Smoking | 2 | NULL |
| 16 | F | No homework | 2 | NULL |
| 17 | F | Disruptive outside classroom | 2 | NULL |
| 18 | F | Eating/drinking in lesson | 1 | NULL |
| 19 | F | Incorrect uniform/equipment | 1 | NULL |
| 20 | F | Phone out in lesson | 3 | NULL |
| 21 | F | Aggressive defiance | 4 | NULL |
| 22 | F | Missed detention | 3 | NULL |
| 23 | F | Inappropriate behaviour/comments | 3 | NULL |
| 32 | F | IT Misuse | NULL | NULL |
| 34 | F | Inappropriate attitude towards staff | NULL | NULL |
| 35 | F | Care & Guidance | NULL | NULL |
+----+------+--------------------------------------+--------+----------+
SELECT * FROM transactions;
+----------------+------------+----------+--------------+--------+-------------+
| Transaction_ID | Datetime | Giver_ID | Recipient_ID | Points | Category_ID |
+----------------+------------+----------+--------------+--------+-------------+
| 34 | 2011-09-07 | 35019 | 137608 | 2 | 1 |
| 35 | 2011-09-07 | 35019 | 139027 | 2 | 1 |
| 36 | 2011-09-07 | 35019 | 139041 | 2 | 1 |
| 37 | 2011-09-07 | 35019 | 139041 | 2 | 1 |
| 38 | 2011-09-07 | 35019 | 139041 | 2 | 1 |
| 39 | 2011-09-07 | 35019 | 139041 | 2 | 1 |
| 40 | 2011-09-07 | 35019 | 137434 | 2 | 1 |
| 41 | 2011-09-07 | 35019 | 137434 | 2 | 1 |
| 42 | 2011-09-07 | 35019 | 137434 | 2 | 1 |
| 43 | 2011-09-07 | 35019 | 137434 | 2 | 1 |
| 44 | 2011-09-07 | 35006 | 137434 | 2 | 1 |
| 45 | 2011-09-07 | 35006 | 90306 | 2 | 1 |
| 46 | 2011-09-07 | 35006 | 90306 | 2 | 1 |
| 47 | 2011-09-07 | 35006 | 90306 | 2 | 1 |
| 48 | 2011-09-07 | 35023 | 137608 | 5 | 2 |
| 49 | 2011-09-07 | 35023 | 139027 | 5 | 2 |
| 50 | 2011-09-07 | 35023 | 139564 | 5 | 2 |
| 51 | 2011-09-07 | 35023 | 139564 | 5 | 2 |
| 52 | 2011-09-07 | 35023 | 139564 | 5 | 2 |
| 53 | 2011-09-07 | 35023 | 137608 | 5 | 3 |
+----------------+------------+----------+--------------+--------+-------------+
SELECT id,UPN,Year_Group,Tutor_Group,SEN_Status,Flags FROM student;
+--------+---------------+------------+-------------+------------+--------+
| id | UPN | Year_Group | Tutor_Group | SEN_Status | Flags |
+--------+---------------+------------+-------------+------------+--------+
| 137608 | A929238400044 | 11 | 11VID | A | |
| 139027 | A929238401045 | 10 | 10KS | | |
| 139041 | A929238402017 | 10 | 10RJ | A | FSM |
| 139892 | A929238403018 | 9 | 9BW | | |
| 139938 | A929238403020 | 9 | 9RH | | |
| 137434 | A929238500027 | 11 | 11VID | | |
| 138832 | A929238502002 | 10 | 10RY | A | FSM,PA |
| 34533 | A929238599028 | 0 | | | PA |
| 139564 | A929241500025 | 12 | | | PA |
| 90306 | A929253100006 | 12 | SLH | A | PA |
+--------+---------------+------------+-------------+------------+--------+