SELECT dept_id, simple_name FROM
(
SELECT t1.dept_id, t1.simple_name, IF(FIND_IN_SET(pid, @pids) > 0, @pids := CONCAT(@pids, ',', dept_id), 0) AS ischild
FROM
(SELECT dept_id, pid, simple_name FROM sys_dept t ORDER BY pid, dept_id) t1,
(SELECT @pids := 1303172963761045505) t2
)
t3
WHERE ischild != 0
==========================================================================================================
PS：還是沒有完全看懂，自測通過，先用着再說；
參考鏈接：
https://blog.csdn.net/Scoful/article/details/106441476
=》Mysql根據某層部門ID查詢所有下級多層子部門