[英]What is a syntax to query a first_name of employees and first_name of their managers?
您通常會從employees
表開始,然后在departments
(他/她所屬的部門)中引入相應的記錄,最后再次加入employees
以獲取部門經理的名字:
select e.firstname employee_firstname, m.firstname manager_first_name
from employees e
inner join departments d on d.department_id = e.department_id
inner join employees m on m.employee_id = d.manager_id
假設 employee.manager_id 指向員工的經理。
然后在 manager_id 上自加入員工表。
SELECT
emp.first_name AS emp_first_name,
mgr.first_name AS mgr_first_name
FROM employees emp
LEFT JOIN employees mgr
ON mgr.employee_id = emp.manager_id
ORDER BY emp.first_name
如果你還想要他們部門的經理。
SELECT
emp.first_name AS emp_first_name,
mgr.first_name AS mgr_first_name,
depmgr.first_name AS depmgr_first_name
FROM employees emp
LEFT JOIN employees mgr
ON mgr.employee_id = emp.manager_id
LEFT JOIN departments dep
ON dep.department_id = emp.department_id
LEFT JOIN employees depmgr
ON depmgr.employee_id = dep.manager_id
ORDER BY emp.first_name
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