mysql-->递归查询

一、为实现查询一级或二级下面的全部级数：
表结构：id 、industry_name、paren_id 

SELECT
                DATA.id
        FROM
        (
        SELECT
        @ids AS _ids,
        ( SELECT @ids := GROUP_CONCAT( id ) FROM sys_industry_type WHERE FIND_IN_SET( parent_id, @ids ) ) AS cids,
        @l := @l + 1 AS LEVEL
        FROM
        sys_industry_type,
        ( SELECT @ids := #{industryId}, @l := 0 ) b
        WHERE
        @ids IS NOT NULL
        ) id,
        sys_industry_type DATA
        WHERE
        FIND_IN_SET( DATA.id, ID._ids ) and parent_id != 0
        ORDER BY level,
        id