MySQL 语句查询所有下级，和一条数据拆分成多条数据

								需求：查询下表中所有的下级


	userid是用户id,  higherid 上级人员的用户Id，

先查询出所有下级

---------------------------------------------------------------SELECT 
	@ids,
	( SELECT @ids := GROUP_CONCAT(userid) 
	FROM dk_user_level 
	WHERE FIND_IN_SET(higherid, @ids) 
	) as cids, 
	@l := @l+1 as lvl 
	FROM dk_user_level, 
	(SELECT @ids := 95, @l := 0 ) b 
	WHERE @ids IS NOT NULL

---

根据“，”号进行切割数据，把一条数据切割为多条数据

    SELECT
    x.*
 
    FROM
    (
    SELECT
    a.type,
    a.`level`,
    substring_index( substring_index( a.cids, ',', b.help_topic_id + 1 ), ',',- 1 ) AS userId
    FROM
    (
    SELECT LEVEL
    ,
    ( SELECT @ids := GROUP_CONCAT( userid ) FROM dk_user_level WHERE FIND_IN_SET( higherid, @ids ) ) AS cids,
    @l := @l + 1 AS type
    FROM
    dk_user_level,
    ( SELECT @ids := 104, @l := 0 ) b
    WHERE
    @ids IS NOT NULL
    ) a
    JOIN mysql.help_topic b ON b.help_topic_id <( length( a.cids ) - length( REPLACE ( a.cids, ',', '' ) ) + 1 )
    ) x

4,加入项目进行处理

    SELECT
    x.*,
   	u.user_name AS userName
    FROM
    (
    SELECT
    a.type,
    a.`level`,
    substring_index( substring_index( a.cids, ',', b.help_topic_id + 1 ), ',',- 1 ) AS userId
    FROM
    (
    SELECT LEVEL
    ,
    ( SELECT @ids := GROUP_CONCAT( userid ) FROM dk_user_level WHERE FIND_IN_SET( higherid, @ids ) ) AS cids,
    @l := @l + 1 AS type
    FROM
    dk_user_level,
    ( SELECT @ids := #{id}, @l := 0 ) b
    WHERE
    @ids IS NOT NULL
    ) a
    JOIN mysql.help_topic b ON b.help_topic_id <( length( a.cids ) - length( REPLACE ( a.cids, ',', '' ) ) + 1 )
    ) x
    LEFT JOIN dk_user u ON x.userId = u.id

    
    1=1
        
       and     x.type=#{type}
        
        
            and     x.type <>#{type}
        
        
         and   x.level=#{level}
        
    

type 1、2、3、4… 是你属于多少层下级

后续会贴出详细的步骤，以及查询所有上级