在SELECT命令中使用CONNECT BY和START WITH子句可以查询表中的树型结构关系。其命令格式如下:
SELECT。。。
CONNECT BY {PRIOR列名1=列名2|列名1=PRIOR裂名2}
[START WITH];
其中:CONNECT BY子句说明每行数据将是按层次顺序检索,并规定将表中的数据连入树型结构的关系中。PRIORY运算符必须放置在连接关系的两列中某一个的前面。对于节点间的父子关系,PRIOR运算符在一侧表示父节点,在另一侧表示子节点,从而确定查找树结构是的顺序是自顶向下还是自底向上。在连接关系中,除了可以使用列名外,还允许使用列表达式。START WITH子句为可选项,用来标识哪个节点作为查找树型结构的根节点。若该子句被省略,则表示所有满足查询条件的行作为根节点。
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
order by pid
从末梢往树ROOT递归
select * from TBL_TEST
start with id=5
connect by prior pid = id
order by id
**************************************************************************
CREATE TABLE xxuts_test_start
(
ID varchar2(100),
NAME VARCHAR2(100)
);
select id,name,level from xxuts_test_start
start with id='A'
connect by prior name=id
order by id
A C 1
A D 1
B E 2
B F 2
C H 2
E G 3
primary_quantity,
primary_unit_of_measure,
source_doc_unit_of_measure,
transaction_type,
parent_transaction_id
FROM rcv_transactions
WHERE invoice_status_code <> 'INVOICED'
-- added trx date range as per gap228 -- rsk 07/12/07
START WITH transaction_id = 276195
CONNECT BY parent_transaction_id = PRIOR transaction_id;
--INTO l_rcv_transaction_id
FROM rcv_transactions
WHERE transaction_type = 'RECEIVE'
START WITH transaction_id = 116231
CONNECT BY transaction_id = PRIOR parent_transaction_id;