Question

我想实现一个查询，使学生（基于搜索）获得的总余额是评估表减去付款表中的金额。

学生姓名-花费（评估）-已支付（付款）-余额总计

表1：学生 id，名字，姓氏，中间名，idno

Sample Data
1, a, a, a, 18001
2, b, b, b, 18002

表2：评估 ID，学生ID，金额

Sample Data
1, 1, 500
2, 1, 600
3, 2, 100
4, 2, 100

表3：付款 ID，学生ID，金额

Sample Data
1, 1, 200
2, 1, 100

结果必须为：

student, assessment, payment, balance
a, 1100, 200, 900
b, 200, 100, 100

这是我当前的查询...，没有得到预期的结果。

$qry = "SELECT c.*, SUM(CASE WHEN x.type = 'assessment' THEN x.amount ELSE 0 END) spent
                             , SUM(CASE WHEN x.type = 'payments' THEN x.amount ELSE 0 END) paid
                             , SUM(CASE WHEN x.type = 'assessment' THEN x.amount ELSE x.amount * -1 END) total
                          FROM students c
                          LEFT JOIN 
                             ( SELECT studentid
                                    , 'assessment' type
                                    , amount
                                 FROM assessment 
                                UNION
                               SELECT studentid
                                    , 'payments'
                                    , amount
                                 FROM payment 
                             ) x
                            ON x.studentid = c.id
                         WHERE ((c.firstname like '%$search%' or c.lastname like '%$search%' or c.middlename like '%$search%' or c.idno like '%$search%') and c.status = 1)
                         GROUP
                            BY c.id;";

Answer 1

在每个子表中为每个学生的每个子表中的金额求和，然后将这些子句与您的主查询结合起来

SELECT c.*,
  COALESCE(a.amount,0) assessment,
  COALESCE(p.amount,0) payment,
  COALESCE(a.amount,0) - COALESCE(p.amount,0) balance
FROM students c
LEFT JOIN (SELECT studentid, SUM(amount) amount 
           FROM assessment
           GROUP BY studentid
) a ON c.id = a.studentid
LEFT JOIN(SELECT studentid, SUM(amount) amount
          FROM payment
          GROUP BY studentid         
) p ON c.id = p.studentid
WHERE ((c.firstname like '%$search%' 
        OR c.lastname like '%$search%' 
        OR c.middlename like '%$search%' 
        OR c.idno like '%$search%') 
       AND c.status = 1)

Demo

MySQL查询从不同的表中扣除两个字段

1 个答案: