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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