php - 这个 SQL 查询有什么问题

Question

我需要找出这个 SQL 有什么问题:

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所有行的计数。所以我认为属性 sql 将如何没有 where 语句。帮助我，我不擅长 SQL。

Answer 1

你必须使用 having cluase 而不是语句末尾的 where:

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