Question

我目前有一个查询，它返回每个客户持有的帐户总数，但我该如何制作，以便只返回拥有多个帐户的客户？

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

Answer 1

您的问题的答案是HAVING。但是，您需要学习使用正确的JOIN语法。简单规则：从不在FROM子句中使用逗号。始终使用明确的JOIN语法。

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;

实际上，您甚至不需要JOIN：

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

这简单得多。

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

请尝试

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

结果的SQL COUNT函数＆＃34;大于或等于＆＃34;

3 个答案: