使用非数字值时出现的无效数错误

Question

我有两个桌子，部门和员工。我想显示department_id、department_name和任何部门中少于4名员工的员工人数。

下面是我使用的代码(我使用，顺便说一句)：

select d.department_id, d.department_name, count(e.last_name)
from departments d, employees e
where e.last_name < 4
group by d.department_id, d.department_name;

但是，我得到了一个无效的数字错误。正确的方法是什么？

Answer 1

这样的事情会更有意义：

SELECT d.department_id,
       d.department_name,
       COUNT(*) AS numEmployees
FROM departments d
INNER JOIN employees e
    ON d.department_id = e.department_id
GROUP BY d.department_id,
         d.department_name
HAVING COUNT(*) < 4