結果「大於或等於」的SQL COUNT函數

Question

我當前有一個查詢，它返回每個客戶持有的帳戶總數，但是如何使其僅返回擁有多個帳戶的客戶？

SELECT C.customerID, COUNT(O.accNumber) AS "total" 
FROM Customer C, Owns O 
WHERE C.customerID = O.customerID 
GROUP BY C.customerID 

Answer 1

回答你的問題是HAVING。但是，您需要學習使用正確的JOIN語法。簡單的規則：從不在FROM條款中使用逗號。 總是使用明確的JOIN語法。

SELECT C.customerID, COUNT(O.accNumber) AS total 
FROM Customer C JOIN 
    Owns O 
    ON C.customerID = O.customerID 
GROUP BY C.customerID 
HAVING COUNT(*) > 1; 

事實上，你甚至都不需要JOIN：

SELECT o.customerID, COUNT(o.accNumber) AS total 
FROM Owns o 
GROUP BY o.customerID 
HAVING COUNT(*) > 1; 

這是簡單得多。

Answer 2

添加HAVING子句

SELECT C.customerID, COUNT(O.accNumber) AS "total" 
FROM Customer C, Owns O 
WHERE C.customerID = O.customerID 
GROUP BY C.customerID 
HAVING COUNT(*) > 1 

Answer 3

請嘗試

WHERE C.customerID = O.customerID AND count(O.accNumber) > 1