Question

我需要找到这个SQL有什么不好的地方：

SELECT DepartmentName, COUNT(*) 
FROM employee,department 
WHERE employee.DepartmentID = department.DepartmentID 
GROUP BY DepartmentName
WHERE COUNT(*)>1

我认为COUNT(*)中的问题是因为它返回了所有行的计数。那么我怎么认为属性sql将没有where语句。帮帮我，我不擅长SQL。

Answer 1

您必须使用having子句而不是声明末尾的位置：

SELECT DepartmentName, COUNT(*) 
FROM employee,department 
WHERE employee.DepartmentID = department.DepartmentID 
GROUP BY DepartmentName
having COUNT(*)>1

Answer 2

SELECT DepartmentName, COUNT(*) AS count
FROM employee,department 
WHERE employee.DepartmentID = department.DepartmentID 
GROUP BY DepartmentName
HAVING count>1;

这个SQL查询有什么问题

2 个答案: