MySql如何利用父id递归向下查询子节点

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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

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