寻找至少有2名员工的部门

Question

我需要使sql问题，它将显示所有部门至少有2个人。

SELECT department.name
FROM department
INNER JOIN employee
ON department.id = employee.department_id
GROUP BY employee.id
HAVING COUNT(employee.id) >= 2;

此查询没有显示任何内容

Answer 1

我认为您在错误的列上使用了GROUP BY 。
如果要计算每个部门的员工，则需要GROUP BY department.id 。

SELECT department.id, department.name, COUNT(employee.id) AS total_employee
FROM department
INNER JOIN employee
ON department.id = employee.department_id
GROUP BY department.id, department.name
HAVING COUNT(employee.id) >= 2;

Answer 2

尝试这个：

SELECT d.name
FROM department d
WHERE
    (SELECT COUNT(*) FROM employee e
    WHERE d.id = e.department_id) >= 2

这样，如果您想更改限制（而不是2，另一个值），查询将起作用。

如果需要，可以使用INNER JOIN ，将来所有没有员工的部门都将无法使用它。