Question

请告诉我以下查询的错误，说cnt是未知列。

SELECT SerialNumber, StoreCode, COUNT(*) as cnt
FROM serialnumberheader
GROUP BY serialnumber, StoreCode
having cnt > 1

Answer 1

在HAVING列表之前评估SELECT子句，因此它不能引用该列别名。

SELECT SerialNumber, StoreCode, COUNT(*) as cnt
FROM serialnumberheader
GROUP BY serialnumber, StoreCode
having COUNT(*) > 1

或者，将查询包装在派生表中：

select SerialNumber, StoreCode, cnt
from
(
    SELECT SerialNumber, StoreCode, COUNT(*) as cnt
    FROM serialnumberheader
    GROUP BY serialnumber, StoreCode
) dt
where cnt > 1

Answer 2

有些（全部？）here不允许您在where和having子句中使用列别名。您可以直接使用别名的表达式：

SELECT   SerialNumber, StoreCode, COUNT(*) AS cnt
FROM     serialnumberheader
GROUP BY SerialNumber, StoreCode
HAVING   COUNT(*) > 1

Answer 3

SELECT   SerialNumber, StoreCode, COUNT(1) AS cnt
FROM     serialnumberheader
GROUP BY SerialNumber, StoreCode
HAVING   COUNT(1) > 1

从SQL中的两列分组的结果中查找重复项

3 个答案: