如何通过内部联接使用分组方式

Question

我有三张桌子的顾客 ， 讨价还价和分期付款 。
我想根据每个客户，并在年底从支付金额的总和减去总价格的总和，从分期付款表中选择从客户表和讨价还价表和支付金额的总和价格的总和名 。
因此结果应为包含所有客户名称及其债务的列表。

我尝试以下命令，但是它返回错误的值，看起来它们被加总了两次甚至更多。

select c.name, b.total_price, i.payment_amount
from customer as c
inner join (select sell_or_buy, sum(total_price) as total_price from     bargains group by C_ID ) as b on (b.sell_or_buy = 'خرید')
inner join (select trade_type, sum(payment_amount) as payment_amount from installment group by C_ID ) as i on (i.trade_type = 'پرداخت')
group by c.C_ID

因为我认为查询求和了分期付款表的每条记录的总价格，并总结了讨价还价表的每条记录的支付金额，所以我尝试在内部联接中使用select来使每个联接与众不同，但这是行不通的，所以无法甚至减去结果。
我也尝试以下查询

select
(select sum(payment_amount) as payment_amount from installment  where trade_type = 'پرداخت'group by C_ID)-
(select sum(total_price) as total_price from bargains where sell_or_buy = 'خرید' group by C_ID)as result

其中显示和错误表示查询返回多行。
当我仅从上面的查询中使用一个选择时，结果是确定的，但是当我尝试将其组合不起作用时。

Answer 1

无需使用子查询来执行此操作，只需将三个表联接并进行聚合，请尝试以下操作：

select 
    c.name,
    sum(b.total_price) as total_price,
    sum(i.payment_amount) as payment_amount
from customer as c
inner join bargains b on c.c_id = b.c_id and b.sell_or_buy = 'خرید'
inner join installment i on c.c_id = i.c_id and i.trade_type = 'پرداخت'
group by c.c_id   -- ,c.name

和喜欢@Tim Biegeleisen表示，如果sql_mode你的MySQL数据库包含ONLY_FULL_GROUP_BY ，你也应该补充c.name在group by子句。 并使用此查询来检查sql_mode ：

show variables like 'sql_mode';

Answer 2

您的原始查询似乎缺少正确的联接条件。 尝试以下方法：

select c.name,
       b.total_price,
       i.payment_amount
from customer as c
inner join
(
    select C_ID, sum(total_price) as total_price
    from bargains
    where sell_or_buy = 'خرید'
    group by C_ID
) as b
    on c.C_ID = b.C_ID
inner join
(
    select C_ID, sum(payment_amount) as payment_amount
    from installment
    where trade_type = 'پرداخت'
    group by C_ID
) as i
    on c.C_ID = i.C_ID

如果要计算总价和付款额之间的差额，则只需使用以下SELECT ：

select c.name,
       b.total_price,
       i.payment_amount,
       b.total_price - i.payment_amount AS diff

Answer 3

您能给我一张每张桌子的实际屏幕截图，其中有几个条目吗？

您可能会因为此行而获得重复的行：内部联接（从C_ID从分期付款组中选择trade_type，sum（payment_amount）作为payment_amount）

基本上，您可能不应该使用sum（）函数，同时还要从任何其他字段中选择值。 原因如下：sum（payment_amount）应该返回正确的1行吗？ 但是在它旁边，您有“ select trade_type”，它可能会返回多行。

还有，这是什么语言？ MySQL的？ SQL吗？

Answer 4

子查询：

SELECT c.Id AS CustomerId, c.Name AS CustomerName, m.Name AS ManagerName, o.SumAmmount 
FROM Customers AS c
INNER JOIN Managers AS m ON c.ManagerId = m.Id
INNER JOIN 
(SELECT SUM(Amount) AS SumAmmount, o.CustomerId
 FROM Orders AS o
 WHERE Date >= '2017-01-01'
 GROUP BY CustomerId
 HAVING SUM(Amount) >= 10000) AS o ON c.Id = o.CustomerId

没有子查询：

SELECT c.Id AS CustomerId, c.Name AS CustomerName, 
       m.Name AS ManagerName, SUM(o.Amount) AS SumAmmount 
FROM Customers AS c
INNER JOIN Managers AS m ON c.ManagerId = m.Id
INNER JOIN Orders AS o ON c.Id = o.CustomerId
WHERE o.Date >= '2017-01-01'
GROUP BY c.Id, c.Name, m.Name
HAVING SUM(Amount) >= 10000