计算两个不同的列的总和的两个表

差

我有命名为出纳，SALES三个不同的表，和REFUNDS计算两个不同的列的总和的两个表

CASHIER表具有：

cashierID/cashier_name

SALES表具有：

salesID/cashierID/amountReceived

REFUNDS表具有：

refundsID/cashierID/amountRefunded

我想显示经由amountReceived从销售和退款接收的收银员的总量和分别amountRefunded列。会有一个MySQL的语法吗？非常感谢！

来源

2012-01-10 mathan0690

SELECT c.cashier_name AS cashier, 
    COALESCE(salesByCashier.totalSales, 0) AS sales, 
    COALESCE(refundsByCashier.totalRefunded, 0) AS refunds, 
    COALESCE(salesByCashier.totalSales, 0) - 
     COALESCE(refundsByCashier.totalRefunded, 0 ) AS total 
FROM 
    cashier c 
LEFT JOIN 
    (SELECT s.cashierID AS cashierID, SUM(amountReceived) AS totalSales 
    FROM sales s 
    GROUP BY s.cashierID) salesByCashier 
ON c.cashierID = salesByCashier.cashierID 
LEFT JOIN 
    (SELECT r.cashierID AS cashierID, SUM(amountRefunded) AS totalRefunded 
    FROM refunds r 
    GROUP BY r.cashierID) refundsByCashier 
ON c.cashierID = refundsByCashier.cashierID

来源

2012-01-10 02:54:41 piotrm

我认为这就是它！非常感谢。但我可以问一个问题，什么是COALESCE（字段1,0）的含义？ – mathan0690 2012-01-10 03:11:57

如果出纳员没有出售或没有返回任何东西，您将从LEFT JOIN获得0而不是NULL。 – piotrm 2012-01-10 03:14:10

好的。再次感谢！ – mathan0690 2012-01-10 03:16:43

select 
    c.cashierID, 
    c.cashier_name, 
    sum(s.amountReceived) as totalReceived, 
    sum(r.amountRefunded) as totalRefunded 
from CASHIER c 
left join SALES s on s.cashierID = c.cashierID 
left join REFUNDS r on r.cashierID = c.cashierID 
group by 1,2

来源

2012-01-10 02:23:59 Bohemian

+1。以略胜一筹的速度击败我。（有趣的是，它甚至包括了与表格相同的别名选择。）:) – 2012-01-10 02:25:08

先生，你会介意我问这个问题吗？在你的小组中，1和2，你是什么意思？你是否将它与第一列和第二列分组？ – 2012-01-10 02:30:48

@johntotetwoo GROUP BY 1,2''是SQL标准缩写，意思是“GROUP BY ,”，即在这种情况下具有与“GROUP BY c.cashierID，c.cashier_name”完全相同的含义。许多人不喜欢这样，但我发现它远远更容易阅读和维护。顺便说一句，你可以列出尽可能多的列号，只要你喜欢什么顺序 – Bohemian 2012-01-10 02:48:20

计算两个不同的列的总和的两个表

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