带有 GROUP CONCAT 和 LEFT JOIN 的行的总和答案

【问题标题】：SUM of rows with GROUP CONCAT and LEFT JOIN带有 GROUP CONCAT 和 LEFT JOIN 的行的总和
【发布时间】：2015-08-26 05:05:15
【问题描述】：

我有一个关于 MySQL 的问题。

我得到了以下表格：

Invoices
invoices_ordermapping
invoices_positions

发票：

id | userid | state
1, 10, 1

invoices_ordermapping

id | invoiceid | orderid
1, 1, Order12
2, 1, Order13

invoices_positions

id | invoiceid | value | text
1, 1, 21, Example
2, 1, 18.9, Example 2

现在我想获取分配给发票的订单（Order12，Order13）和总金额（Sum of value）。

这是我期望的结果：

Invoiceid | Orders | Sum
1, Order12, Order13, 39.9

我正在使用这个 MySQL 查询：

SELECT group_concat(DISTINCT orderid ORDER BY orderid SEPARATOR ", ") AS orderid, 
       SUM(ip.total) as value
FROM tbl_invoices as a
LEFT JOIN tbl_invoices_ordermapping as oi ON oi.invoiceid = a.id 
LEFT JOIN tbl_invoices_positions as ip on ip.invoiceid = oi.invoiceid          
GROUP BY oi.invoiceid
ORDER BY oi.invoiceid

不幸的是我得到了这个结果：

Orderid: Order12, Order12, Order13, Order13
Value: 119.69999885559082

我在这里做错了什么？

【问题讨论】：

标签： mysql sum left-join concat

【解决方案1】：

我认为您想要以下内容：

SELECT a.id AS InvoiceId, Orders, `Sum`
FROM Invoices as a
LEFT JOIN (SELECT invoiceid,
                  GROUP_CONCAT(DISTINCT orderid 
                               ORDER BY orderid SEPARATOR ', ') AS Orders
           FROM Invoices_ordermapping 
           GROUP BY invoiceid ) AS oi ON oi.invoiceid = a.id
LEFT JOIN (SELECT invoiceid, SUM(`value`) as `Sum`
           FROM Invoices_positions
           GROUP BY invoiceid) AS ip ON ip.invoiceid = a.id
ORDER BY a.id

您的查询的问题在于LEFT JOINs 复制了Invoices_positions 行，因此，SUM 是根据表中相同行的多次出现计算得出的。

您需要先对Invoices_ordermapping 和Invoices_positions 表执行聚合，然后加入Invoices 表。

Fiddle Demo here

【讨论】：