参考地址：https://www.cnblogs.com/biehongli/p/9391757.html
1、表结构
2、案例数据
3、查询语句
（1）、模板
SELECT * FROM ( SELECT @r AS _id, (SELECT @r := parent_id FROM table_name WHERE id = _id) AS parent_id, @l := @l + 1 AS lvl FROM (SELECT @r := 子id, @l := 0) vars, table_name h WHERE @r <> 0) T1 JOIN table_name T2 ON T1._id = T2.id ORDER BY T1.lvl DESC
（2）、栗子
SELECT T2.id,T2.name,T2.level,T2.parent_id,T2.level_name FROM ( SELECT @r AS _id, (SELECT @r := parent_id FROM tbl_industry_type WHERE id = _id) AS parent_id, @l := @l + 1 AS lvl FROM (SELECT @r := 7, @l := 0) vars, tbl_industry_type h WHERE @r <> 0) T1 JOIN tbl_industry_type T2 ON T1._id = T2.id ORDER BY T1.lvl DESC
（3）、查询结果
