Question

我正在使用以下查询从我的数据库的不同表中获取报告，请检查以下内容......

SELECT s.id, s.name, c.name AS course_name,
s.open_bal AS open_balance, sum(i.amount) AS gross_fee,
sum(i.discount) AS discount, sum(i.amount) - sum(i.discount) AS net_payable,
SUM(r.reg_fee+r.tut_fee+r.other_fee) AS net_recieved,
(sum(i.amount) - sum(i.discount)) - SUM(r.reg_fee+r.tut_fee+r.other_fee) AS balance_due
FROM students s
INNER JOIN courses c on c.id = s.course_id
LEFT JOIN invoices i on i.student_id = s.id
LEFT JOIN recipts r on r.student_id = s.id;

发票

| id | student_id | amount   | discount |  dnt        | 
+----+------------+----------+----------+-------------+
| 2  | 22         | 35000    | 0        |  2011/01/01 |
+----+------------+----------+----------+-------------+

未从gross_fee和net_payable获取正确的值。

感谢。

Answer 1

鉴于选择中的SUM，我认为GROUP BY s.id应该做到这一点。无论如何，GROUP BY似乎缺失了：）

SELECT s.id, s.name, c.name AS course_name,
s.open_bal AS open_balance,
SUM(r.reg_fee+r.tut_fee+r.other_fee) AS net_recieved,
 (sum(i.amount) - sum(i.discount)) - SUM(r.reg_fee+r.tut_fee+r.other_fee) AS balance_due
FROM students s
INNER JOIN courses c on c.id = s.course_id
LEFT JOIN invoices i on i.student_id = s.id
LEFT JOIN recipts r on r.student_id = s.id
GROUP BY s.id;

修改

单独查询，允许检索所有发票的 gross_fee 和 net_payable

SELECT sum(amount) AS gross_fee,
  sum(discount) AS discount,
  sum(amount) - sum(discount) AS net_payable,
FROM invoices;

Answer 2

是否有两个学生记录都获得了s.course_id的值？

你有从学生到课程的内心联系......

INNER JOIN课程c c.id = s.course_id

如果s.course_id在其中一个学生记录中为空，则查询将只返回一行。

mysql INNER JOIN

2 个答案: