MySql利用父id递归向下查询子节点的方法实例

不用写存储过程，不用建数据库函数，一段sql就可以实现不用写存储过程，不用建数据库函数，一段sql就可以实现不用写存储过程，不用建数据库函数，一段sql就可以实现SELECTID.LEVEL,DATA...

不用写存储过程，不用建数据库函数，一段sql就可以实现

不用写存储过程，不用建数据库函数，一段sql就可以实现

不用写存储过程，不用建数据库函数，一段sql就可以实现

SELECT
ID.LEVEL,
DATA.* 
FROM
(
SELECT
@ids AS _ids,
( SELECT @ids := GROUP_CONCAT( region_id ) FROM region WHERE FIND_IN_SET(parent_id, @ids ) ) AS cids,
@l := @l + 1 AS LEVEL 
FROM
region,
( SELECT @ids := 3, @l := 0 ) b 
WHERE
@ids IS NOT NULL 
) ID,
region DATA 
WHERE
FIND_IN_SET( DATA.region_id, ID._ids ) 
ORDER BY
LEVEL

测试

--创建测试环境
create table t_test(
id int PRIMARY key,
parent_id int,
name varchar(200)
)

insert t_test VALUES(1,null,"中国");

insert t_test VALUES(2,1,"华北");

insert t_test VALUES(3,2,"山西省");
insert t_test VALUES(4,2,"北京");

insert t_test VALUES(5,3,"临汾市");
insert t_test VALUES(6,4,"北京市");


insert t_test VALUES(7,5,"尧都区");
insert t_test VALUES(8,6,"朝阳区");

insert t_test VALUES(9,7,"解放西路");
insert t_test VALUES(10,8,"朝阳北路");


SELECT * FROM t_test;

测试数据展示

查询 id=1，查询中国下边有哪些地方

SELECT
ID.LEVEL,
DATA.* 
FROM
(
SELECT
@ids AS _ids,
( SELECT @ids := GROUP_CONCAT( id ) FROM t_test WHERE FIND_IN_SET(parent_id, @ids ) ) AS cids,
@l := @l + 1 AS LEVEL 
FROM
t_test,
( SELECT @ids := 1, @l := 0 ) b 
WHERE
@ids IS NOT NULL 
) ID,
t_test DATA 
WHERE
FIND_IN_SET( DATA.id, ID._ids ) 
ORDER BY
LEVEL

id=3，查询山西下边有哪些地方

SELECT
ID.LEVEL,
DATA.* 
FROM
(
SELECT
@ids AS _ids,
( SELECT @ids := GROUP_CONCAT( id ) FROM t_test WHERE FIND_IN_SET(parent_id, @ids ) ) AS cids,
@l := @l + 1 AS LEVEL 
FROM
t_test,
( SELECT @ids := 3, @l := 0 ) b 
WHERE
@ids IS NOT NULL 
) ID,
t_test DATA 
WHERE
FIND_IN_SET( DATA.id, ID._ids ) 
ORDER BY
LEVEL

id=4，查询北京下边有哪些地方

最后再从 id=2 华北地区往下查询

总结 

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