mysql根据父节点递归查询所有子节点

mysql根据父节点递归查询所有子节点，以此备录。

根据一个父节点查询所有子节点（包含自身）

SELECT au.id 
FROM (SELECT * FROM t_app_user WHERE parent_id IS NOT NULL) au,
     (SELECT @pid := '1') pd 
WHERE FIND_IN_SET(parent_id, @pid) > 0 
  AND @pid := concat(@pid, ',', id)
union select id from t_app_user where id = '1';

根据多个父节点查询所有子节点（包含自身）

SELECT au.id 
FROM (SELECT * FROM t_app_user WHERE parent_id IS NOT NULL) au,
     (SELECT @pid := '1,4') pd 
WHERE FIND_IN_SET(parent_id, @pid) > 0 
  AND @pid := concat(@pid, ',', id) 
union select id from t_app_user where FIND_IN_SET(id,@pid) > 0;

如果不想查询结果包含自身，去掉后边的union