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