Oracle用Start with...Connect By子句递归查询

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。
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
select * from TBL_TEST
 start with id=1
 connect by prior id = pid
         and id!=pid
 
从末梢往树ROOT递归
select * from TBL_TEST
 start with id=5
 connect by prior pid = id
          and id!=pid

 

--直接得到指定节点的根节点
SELECT DISTINCT CONNECT_BY_ROOT T.JDID AS ROOT
  FROM YH_DW T
 --WHERE T.JDID = '1231'
 START WITH T.JDID = T.SJJDID
CONNECT BY PRIOR T.JDID = T.SJJDID
       AND T.JDID != T.SJJDID