ITPub博客

首页 > Linux操作系统 > Linux操作系统 > Oracle Connect By Prior用法

Oracle Connect By Prior用法

原创 Linux操作系统 作者:beret595 时间:2011-10-20 20:37:52 0 删除 编辑

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
where
start with
connect by
;

:过滤条件,用于对返回的所有记录进行过滤。
:查询结果重起始根结点的限定条件。
:连接条件

数据组织结构如下图:

 

Oracle Connect By Prior用法 - ekong - 仰天一笑泪光寒500)this.width=500;" border="0">


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;
 

Oracle Connect By Prior用法 - ekong - 仰天一笑泪光寒500)this.width=500;" border="0">


获取特定子树:
select * from t2 start with id = 1 connect by prior id = root_id;

Oracle Connect By Prior用法 - ekong - 仰天一笑泪光寒500)this.width=500;" border="0">

 
select * from t2 start with id = 4 connect by prior id = root_id;

Oracle Connect By Prior用法 - ekong - 仰天一笑泪光寒500)this.width=500;" border="0">

 

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;

Oracle Connect By Prior用法 - ekong - 仰天一笑泪光寒500)this.width=500;" border="0">

 

select * from t2 start with id = 1 connect by id = root_id;
如:

Oracle Connect By Prior用法 - ekong - 仰天一笑泪光寒500)this.width=500;" border="0">

来自 “ ITPUB博客 ” ,链接:http://blog.itpub.net/13332800/viewspace-709431/,如需转载,请注明出处,否则将追究法律责任。

请登录后发表评论 登录
全部评论

注册时间:2011-07-28

  • 博文量
    16
  • 访问量
    24796