oracle递归查询

转自:虫二的专栏 http://blog.csdn.net/xzknet/archive/2008/05/06/2404559.aspx
Select * from …. Where [结果过滤条件语句]

Start with  [and起始条件过滤语句]

Connect by prior [and中间记录过滤条件语句]

一、Start with.........Connect By 子句

START WITH specifies the root row(s) of the hierarchy.
CONNECT BY specifies the relationship between parent rows and child rows of the hierarchy. In a hierarchical query, one expression in condition must be qualified with the PRIOR operator to refer to the parent row
二、示例

1. 创建测试表：

CREATE TABLE TBL_TEST
(
  ID    NUMBER,
  NAME  VARCHAR2(100 BYTE),
  PID   NUMBER                                  DEFAULT 0
);

2.插入测试数据：

INSERT INTO TBL_TEST(ID,NAME,PID) VALUES('1','10','0');
INSERT INTO TBL_TEST(ID,NAME,PID) VALUES('1','11','1');
INSERT INTO TBL_TEST(ID,NAME,PID) VALUES('3','20','0');
INSERT INTO TBL_TEST(ID,NAME,PID) VALUES('4','12','1');
INSERT INTO TBL_TEST(ID,NAME,PID) VALUES('5','121','2');

3.上述单表情况一般用于维护树型结构的应用

从Root往树末梢递归

select * from TBL_TEST t 
start with t.id=1
connect by prior t.id = t.pid

从末梢往树ROOT递归

select * from TBL_TEST
start with id=5
connect by prior pid = id

start with 后面跟着树根，定义了树开始显示的起点位置，如上面两种查询，不管从树根到树顶，还是从树顶到树根。

5.排除单一体及其分支

select t.* from TBL_TEST t
start with t.id=1
connect by prior pid = id
and id != 2

这个语句表示从id为2的开始，包括后面的子分支，全部排除

注意：这里和where条件的过虑方式不一样，where条件只是把相应的某条不符合要求的记录排除。