create table area_test( id number(10) not null, parent_id number(10), name varchar2(255) not null ); alter table area_test add (constraint district_pk primary key (id)); insert into area_test (ID, PARENT_ID, NAME) values (1, null, "中国"); insert into area_test (ID, PARENT_ID, NAME) values (11, 1, "河南省"); insert into area_test (ID, PARENT_ID, NAME) values (12, 1, "北京市"); insert into area_test (ID, PARENT_ID, NAME) values (111, 11, "郑州市"); insert into area_test (ID, PARENT_ID, NAME) values (112, 11, "平顶山市"); insert into area_test (ID, PARENT_ID, NAME) values (113, 11, "洛阳市"); insert into area_test (ID, PARENT_ID, NAME) values (114, 11, "新乡市"); insert into area_test (ID, PARENT_ID, NAME) values (115, 11, "南阳市"); insert into area_test (ID, PARENT_ID, NAME) values (121, 12, "朝阳区"); insert into area_test (ID, PARENT_ID, NAME) values (122, 12, "昌平区"); insert into area_test (ID, PARENT_ID, NAME) values (1111, 111, "二七区"); insert into area_test (ID, PARENT_ID, NAME) values (1112, 111, "中原区"); insert into area_test (ID, PARENT_ID, NAME) values (1113, 111, "新郑市"); insert into area_test (ID, PARENT_ID, NAME) values (1114, 111, "经开区"); insert into area_test (ID, PARENT_ID, NAME) values (1115, 111, "金水区"); insert into area_test (ID, PARENT_ID, NAME) values (1121, 112, "湛河区"); insert into area_test (ID, PARENT_ID, NAME) values (1122, 112, "舞钢市"); insert into area_test (ID, PARENT_ID, NAME) values (1123, 112, "宝丰市"); insert into area_test (ID, PARENT_ID, NAME) values (11221, 1122, "尚店镇");
select * from area_test start with name ="郑州市" connect by prior id=parent_id
select t.*,level from area_test t start with name ="郑州市" connect by prior t.parent_id=t.id order by level asc;
start with 子句:遍历起始条件,如果要查父结点,这里可以用子结点的列,反之亦然。
connect by 子句:连接条件。prior 跟父节点列parentid放在一起,就是往父结点方向遍历;prior 跟子结点列subid放在一起,则往叶子结点方向遍历。parent_id、id两列谁放在“=”前都无所谓,关键是prior跟谁在一起。
order by 子句:排序。
select d.*, connect_by_root(d.id) rootid, connect_by_root(d.name) rootname from area_test d where name="二七区" start with d.parent_id IS NULL connect by prior d.id=d.parent_id
select id, parent_id, name, sys_connect_by_path(name, "->") namepath, level from area_test start with name = "平顶山市" connect by prior id = parent_id
with tmp(id, parent_id, name) as ( select id, parent_id, name from area_test where name = "平顶山市" union all select d.id, d.parent_id, d.name from tmp, area_test d where tmp.id = d.parent_id ) select * from tmp;
with tmp(id, parent_id, name) as ( select id, parent_id, name from area_test where name = "二七区" union all select d.id, d.parent_id, d.name from tmp, area_test d where tmp.parent_id = d.id ) select * from tmp;
我们称表中的数据存在父子关系,通过列与列来关联的,这样的数据结构为树结构。
现在有一个menu表,字段有id,pid,title三个。
查询菜单id为10的所有子菜单。
SELECT * FROM tb_menu m START WITH m.id=10 CONNECT BY m.pid=PRIOR m.id;
将PRIOR关键字放在m.id前面,意思就是查询pid是当前记录id的记录,如此顺延找到所有子节点。
查询菜单id为40的所有父菜单。
SELECT * FROM tb_menu m START WITH m.id=40 CONNECT BY PRIOR m.pid= m.id ORDER BY ID;
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