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
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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