SYS_CONNECT_BY_PATH函数用法 ORACLE

SYS_CONNECT_BY_PATH函数用法 ORACLE

SELECT ename   

FROM scott.emp    

START WITH ename = 'KING'    

CONNECT BY PRIOR empno = mgr;    

  

--得到结果为：   

  

KING   

JONES   

SCOTT   

ADAMS   

FORD   

SMITH   

BLAKE   

ALLEN   

WARD   

MARTIN   

TURNER   

JAMES   

  

  

  

而：   

  

  

  

SELECT SYS_CONNECT_BY_PATH(ename, '>') "Path"    

FROM scott.emp    

START WITH ename = 'KING'    

CONNECT BY PRIOR empno = mgr;   

  

  

  

--得到结果为：   

  

  

  

>KING   

>KING>JONES   

>KING>JONES>SCOTT   

>KING>JONES>SCOTT>ADAMS   

>KING>JONES>FORD   

>KING>JONES>FORD>SMITH   

>KING>BLAKE   

>KING>BLAKE>ALLEN   

>KING>BLAKE>WARD   

>KING>BLAKE>MARTIN   

>KING>BLAKE>TURNER   

>KING>BLAKE>JAMES   

>KING>CLARK   

>KING>CLARK>MILLER  

SELECT ename

FROM scott.emp 

START WITH ename = 'KING' 

CONNECT BY PRIOR empno = mgr;
--得到结果为：
KING

JONES

SCOTT

ADAMS

FORD

SMITH

BLAKE

ALLEN

WARD

MARTIN

TURNER

JAMES
 
而：
 
SELECT SYS_CONNECT_BY_PATH(ename, '>') "Path" 

FROM scott.emp 

START WITH ename = 'KING' 

CONNECT BY PRIOR empno = mgr;
 
--得到结果为：
 
>KING

>KING>JONES

>KING>JONES>SCOTT

>KING>JONES>SCOTT>ADAMS

>KING>JONES>FORD

>KING>JONES>FORD>SMITH

>KING>BLAKE

>KING>BLAKE>ALLEN

>KING>BLAKE>WARD

>KING>BLAKE>MARTIN

>KING>BLAKE>TURNER

>KING>BLAKE>JAMES

>KING>CLARK

>KING>CLARK>MILLER

 

其实SYS_CONNECT_BY_PATH这个函数是oracle9i才新提出来的！

它一定要和connect by子句合用！

第一个参数是形成树形式的字段，第二个参数是父级和其子级分隔显示用的分隔符！
START WITH 代表你要开始遍历的的节点！
CONNECT BY PRIOR 是标示父子关系的对应！
如下例子：
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select max(   

substr(   

sys_connect_by_path(column_name,',')   

,2)   

)   

from (select column_name,rownum rn from user_tab_columns where table_name ='AA_TEST')   

start with rn=1 connect by rn=rownum ;  

select max(

substr(

sys_connect_by_path(column_name,',')

,2)

)

from (select column_name,rownum rn from user_tab_columns where table_name ='AA_TEST')

start with rn=1 connect by rn=rownum ;
 
是将列用,进行分割成为一行，然后将首个，去掉，只取取最大的那个数据。
－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－
下面是别人的例子：
1、带层次关系
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SQL> create table dept(deptno number,deptname varchar2(20),mgrno number);   

  

Table created.   

  

SQL> insert into dept values(1,'总公司',null);   

  

1 row created.   

  

SQL> insert into dept values(2,'浙江分公司',1);   

  

1 row created.   

  

SQL> insert into dept values(3,'杭州分公司',2);   

  

1 row created.   

  

SQL> commit;   

  

Commit complete.   

  

SQL> select max(substr(sys_connect_by_path(deptname,','),2)) from dept connect by prior deptno=mgrno;   

  

MAX(SUBSTR(SYS_CONNECT_BY_PATH(DEPTNAME,','),2))   

--------------------------------------------------------------------------------   

总公司,浙江分公司,杭州分公司  

SQL> create table dept(deptno number,deptname varchar2(20),mgrno number);
Table created.
SQL> insert into dept values(1,'总公司',null);
1 row created.
SQL> insert into dept values(2,'浙江分公司',1);
1 row created.
SQL> insert into dept values(3,'杭州分公司',2);
1 row created.
SQL> commit;
Commit complete.
SQL> select max(substr(sys_connect_by_path(deptname,','),2)) from dept connect by prior deptno=mgrno;
MAX(SUBSTR(SYS_CONNECT_BY_PATH(DEPTNAME,','),2))

--------------------------------------------------------------------------------

总公司,浙江分公司,杭州分公司
2、行列转换

如把一个表的所有列连成一行，用逗号分隔:
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SQL> select max(substr(sys_connect_by_path(column_name,','),2))   

from (select column_name,rownum rn from user_tab_columns where table_name ='DEPT')   

start with rn=1 connect by rn=rownum ;   

  

MAX(SUBSTR(SYS_CONNECT_BY_PATH(COLUMN_NAME,','),2))   

--------------------------------------------------------------------------------   

DEPTNO,DEPTNAME,MGRNO