我如何子查询两个连接？答案

【问题标题】：How do i sub query two joins?我如何子查询两个连接？
【发布时间】：2016-10-05 21:23:03
【问题描述】：

我创建了两个查询，它们都返回彼此独立的所需结果。我正在尝试加入他们以使返回的值为 customerName、Amount Ordered 和 Amount Paid。

目前，此查询有效，但仅返回 customerName。如何让查询返回其他两列？

SELECT c1.customerName
FROM 
    (SELECT cc.customerName, ROUND(SUM(od.priceEach * od.quantityOrdered), 2) as '$ Amount Ordered'
     FROM customers cc
     INNER JOIN orders o ON o.customerNumber = cc.customerNumber
     INNER JOIN orderdetails od ON od.orderNumber = o.orderNumber
     GROUP BY cc.customerName
    ) c1
 INNER JOIN
    (SELECT c.customerName, ROUND(SUM(p.amount), 2) as 'Total $ Amount Paid'
     FROM customers c
     INNER JOIN payments p ON p.customerNumber = c.customerNumber
     GROUP BY c.customerName
    ) c2
WHERE c1.customerName = c2.customerName
GROUP BY c1.customerName
ORDER BY c1.customerName;

【问题讨论】：

标签： mysql join subquery

【解决方案1】：

这应该选择其他列

SELECT c1.customerName, c1.Amount_Ordered as '$ Amount Ordered', c2.Total_Amount_Paid  as 'Total $ Amount Paid'
FROM 
    (SELECT cc.customerName, ROUND(SUM(od.priceEach * od.quantityOrdered), 2) as Amount_Ordered
     FROM customers cc
     INNER JOIN orders o ON o.customerNumber = cc.customerNumber
     INNER JOIN orderdetails od ON od.orderNumber = o.orderNumber
     GROUP BY cc.customerName
    ) c1
 INNER JOIN
    (SELECT c.customerName, ROUND(SUM(p.amount), 2) as  Total_Amount_Paid
     FROM customers c
     INNER JOIN payments p ON p.customerNumber = c.customerNumber
     GROUP BY c.customerName
    ) c2
WHERE c1.customerName = c2.customerName
GROUP BY c1.customerName
ORDER BY c1.customerName;

【讨论】：

【解决方案2】：

只需将它们添加到选择部分：

SELECT c1.customerName, C1.amountOrdered, C2.amountPaid FROM ...

还有一点建议 - 不要在列名中使用空格或 $ 等特殊符号，这是不好的做法。我认为mySql甚至允许它是一个错误

【讨论】：

感谢您的提示。我不知道，因为我是 SQL 新手。