使用单个查询连接三个表

Question

我有三张桌子，我想加入它们。

连接两个表完美，但连接三个表 returns 仅一行

Table 姓名

用户详细信息
销售轨道
付款详情

查询 #1：

SELECT  
    `userdetails`.CustomerIndex, 
    `userdetails`.FristName,
    SUM(`paymentdetails`.Amountofpaying) TotalPaid
FROM
    `userdetails`
LEFT JOIN 
    `paymentdetails` ON `userdetails`.CustomerIndex=`paymentdetails` .CustomerID
GROUP BY 
    `userdetails`.CustomerIndex,`userdetails`.FristName

查询#2：

SELECT  
    `userdetails`.CustomerIndex, 
    `userdetails`.FristName,
    SUM(`saletrack`.Total) Totalbilled
FROM 
    `userdetails`
LEFT JOIN 
    `saletrack` ON `userdetails`.CustomerIndex = `saletrack`.CustomerId
GROUP BY 
    `userdetails`.CustomerIndex, `userdetails`.FristName

查询 #3：

SELECT 
    s.CustomerId, 
    SUM(s.Total) Totalbilled, 
    p.CustomerID, 
    SUM(p.Amountofpaying) TotalPaid
FROM  
    `userdetails` AS ud
LEFT JOIN 
    `saletrack` AS s ON ud.CustomerIndex = s.CustomerId
LEFT JOIN 
    `paymentdetails` AS p ON ud.CustomerIndex = p.CustomerID
WHERE 
    p.CustomerID = ud.CustomerIndex
    AND s.CustomerId = ud.CustomerIndex
LIMIT 0 , 30

Answer 1

正如您在连接中提到的 ud.CustomerIndex = s.CustomerId && ud.CustomerIndex = p.CustomerID 那么无需输入又是哪里条件。试试这个：

SELECT s.CustomerId, SUM( s.Total ) Totalbilled, p.CustomerID, SUM( p.Amountofpaying ) TotalPaid
FROM  `userdetails` AS ud
LEFT JOIN  `saletrack` AS s ON ud.CustomerIndex = s.CustomerId
LEFT JOIN  `paymentdetails` AS p ON ud.CustomerIndex = p.CustomerID
LIMIT 0 , 30

Answer 2

我们需要添加按查询分组

SELECT s.CustomerId, SUM( s.Total ) Totalbilled, p.CustomerID, SUM( p.Amountofpaying ) TotalPaid
FROM  `userdetails` AS ud
LEFT JOIN  `saletrack` AS s ON ud.CustomerIndex = s.CustomerId
LEFT JOIN  `paymentdetails` AS p ON ud.CustomerIndex = p.CustomerID
WHERE p.CustomerID = ud.CustomerIndex
AND s.CustomerId = ud.CustomerIndex
***GROUP BY ud.CustomerIndex, ud.FristName***
LIMIT 0 , 30

使用单个查询连接三个表

Join three tables using single query

mysql

sql

sql-server

left-join