Start with...Connect By

Start with...Connect By

Start with...Connect By子句递归查询一般用于一个表维护树形结构的应用。（即递归查询）

一个使用实例，创建示例表：

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

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('2','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');

从Root往树末梢递归 （取全部“子孙”集）:

SELECT * FROM TBL_TEST
start WITH id=1
connect BY prior id = pid
ORDER BY pid

从末梢往树ROOT递归（取全部“父爷”集）:

SELECT * FROM TBL_TEST
start WITH id=5
connect BY prior pid = id
ORDER BY id