-引用别人的表结构
create table test_connect_by (child number,parent number);
insert into TEST_CONNECT_BY (CHILD, PARENT)
values (2, 5);
insert into TEST_CONNECT_BY (CHILD, PARENT)
values (3, 5);
insert into TEST_CONNECT_BY (CHILD, PARENT)
values (10, 15);
insert into TEST_CONNECT_BY (CHILD, PARENT)
values (5, 15);
insert into TEST_CONNECT_BY (CHILD, PARENT)
values (9, 17);
insert into TEST_CONNECT_BY (CHILD, PARENT)
values (8, 17);
insert into TEST_CONNECT_BY (CHILD, PARENT)
values (15, 38);
insert into TEST_CONNECT_BY (CHILD, PARENT)
values (17, 38);
insert into TEST_CONNECT_BY (CHILD, PARENT)
values (6, 38);
insert into TEST_CONNECT_BY (CHILD, PARENT)
values (13, 26);
insert into TEST_CONNECT_BY (CHILD, PARENT)
values (1, 26);
insert into TEST_CONNECT_BY (CHILD, PARENT)
values (12, 26);
insert into TEST_CONNECT_BY (CHILD, PARENT)
values (11, 18);
insert into TEST_CONNECT_BY (CHILD, PARENT)
values (7, 18);
insert into TEST_CONNECT_BY (CHILD, PARENT)
values (38, null);
insert into TEST_CONNECT_BY (CHILD, PARENT)
values (26, null);
insert into TEST_CONNECT_BY (CHILD, PARENT)
values (18, null);
commit;
---------------------------------------
select a.child,
a.parent,
level "层次",
sys_connect_by_path(child, '->') "合并层次",
prior a.child "父节点",
connect_by_root a.child "根节点",
decode(connect_by_isleaf, 1, a.child, null) "子节点",
decode(connect_by_isleaf, 1, '是', '否') "是否子节点"
from test_connect_by a
start with a.parent is null --从parent为空开始扫描
connect by prior a.child = a.parent --以child为父列连接parent
order siblings by child desc --对层次排序
;
转贴：
Oracle Connect By用法
oracle中的select语句可以用START WITH...CONNECT BY PRIOR子句实现递归查询，connect by 是结构化查询中用到的，其基本语法是：
select ... from <TableName>
where <Conditional-1>
start with <Conditional-2>
connect by <Conditional-3>
;
<Conditional-1>：过滤条件，用于对返回的所有记录进行过滤。
<Conditional-2>：查询结果重起始根结点的限定条件。
<Conditional-3>：连接条件
数据组织结构如下图：
数据库表结构如下：
create table t2(
root_id number,
id number,
name varchar(5),
description varchar(10)
);
insert into t2(root_id,id,name,description) values(0,1,'a','aaa');
insert into t2(root_id,id,name,description) values(1,2,'a1','aaa1');
insert into t2(root_id,id,name,description) values(1,3,'a2','aaa2');
insert into t2(root_id,id,name,description) values(0,4,'b','bbb');
insert into t2(root_id,id,name,description) values(4,5,'b1','bbb1');
insert into t2(root_id,id,name,description) values(4,6,'b2','bbb2');
获取完整树：
select * from t2 start with root_id = 0 connect by prior id = root_id;
获取特定子树：
select * from t2 start with id = 1 connect by prior id = root_id;
select * from t2 start with id = 4 connect by prior id = root_id;
如果connect by prior中的prior被省略，则查询将不进行深层递归。
如：
select * from t2 start with root_id = 0 connect by id = root_id;
select * from t2 start with id = 1 connect by id = root_id;
如：
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