Question

我有这个运行得很好的查询：

SELECT offers.*, COALESCE(SUM(commission),0) AS revenue, COUNT(commission) AS leads
FROM offers
LEFT JOIN offers_revenue AS or ON or.offerid=offers.offerid
GROUP BY offers.offerid

这将返回商品表中的所有行，并添加了正确的商品。

现在我需要添加一个where子句（比方说，当满足某个条件时不要SUM）：

SELECT offers.*, COALESCE(SUM(commission),0) AS revenue, COUNT(commission) AS leads, reversed
FROM offers
LEFT JOIN offers_revenue AS or ON or.offerid=offers.offerid
WHERE reversed=0
GROUP BY offers.offerid, reversed

首先我尝试添加WHERE子句，但是这给我留下了一组空的结果，在挖掘之后我了解到你需要在GROUP BY中包含where参数并将它们包含在SELECT ...中但是仍然没有结果。

我在这里做错了什么？在第一个查询中，我的测试表上的所有结果都设置为reverse = 0，所以我必须在这里遗漏一些东西。

Answer 1

尝试使用IF语句：

  SELECT offers.*, if(reversed=0 , 0 , SUM(commission)) ) AS revenue, 

        COUNT(commission) AS leads, 
        reversed                 
 FROM offers
 LEFT JOIN offers_revenue AS or ON or.offerid=offers.offerid
 GROUP BY offers.offerid, reversed

Answer 2

据推测，reversed位于or表中。您通过比较将left outer join变为inner join。解决方案是将条件移动到on子句：

SELECT o.*, COALESCE(SUM(ofr.commission),0) AS revenue, COUNT(ofr.commission) AS leads, reversed
FROM offers o LEFT JOIN
     offers_revenue ofr
     ON `ofr`.offerid = o.offerid and ofr.reversed = 0
GROUP BY o.offerid;

MYSQL GROUP BY和WHERE子句

2 个答案: