MYSQL GROUP BY和WHERE子句

Question

我有這樣的查詢運行得很好：

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 

這將返回我的所有與正確comission報價表中的行相加。

現在我需要添加一個WHERE子句（可以說，當某個條件滿足並不總和）：

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 

開始我嘗試只需添加WHERE子句，但是這回我一個空集的結果，挖掘後我知道，你需要包括你的GROUP BY參數，並將它們包括在SELECT中，但仍然沒有結果。

我在這裏做錯了什麼？在第一個查詢中，我測試表上的所有結果都被設置爲reverse = 0，所以我必須在這裏丟失一些東西。

Answer 1

想必reversed是在or表。您通過比較將left outer join變成inner join。該解決方案是將條件移到on條款：

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; 

Answer 2

嘗試這與IF statment：

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