如何显示所有经理的姓氏和号码以及他/她的下属的员工人数

Question

这是模式

，我试着用内嵌，但结果都是垃圾

SELECT
     employees.last_name   AS last_name,
     COUNT(employees.job_id) AS EMPLOYEES_Subordinates,
     COUNT(employees.manager_id) AS Manager_Numbers
 FROM
     employees left
     JOIN departments ON departments.manager_id = employees.manager_id
 GROUP BY
     employees.last_name
 ORDER BY
 EMPLOYEES_Subordinates desc;

(我真的不知道如何向你展示人力资源部的表格)如果任何一个人都有甲骨文数据库的人力资源，并且有时间帮我，我很高兴。

Answer 1

不太确定，但是尝试一下这样的方法：

SELECT 
    e.LAST_NAME
    ,(SELECT COUNT(ee.EMPLOYEE_ID) FROM EMPLOYEES ee WHERE ee.MANAGER_ID = e.EMPLOYEE_ID) AS 'NUMBER OF WORKERS'
FROM EMPLOYEES e
WHERE MANAGER_ID IS NULL