Oracle層次查詢 connect by prior

1、表格初始化指令碼

https://download.csdn.net/download/newbie_907486852/10838835

2、connect by遞迴呼叫

select rownum,rownum+1,rownum+2 from dual connect by rownum <=110000;

select rownum,rownum+1,rownum+2 from dual where rownum <=110000;
 

3、connect by層級查詢

select empno,mgr, ename, job, hiredate, sal, comm, deptno, level as lv
from emp
start with empno = 7839
connect by (prior empno) = mgr;


prior 在 empno前表示對empno進行升序
prior 在 empno後表示對empno進行降序
start with empno = 7839表示從這個開始查詢
connect by (prior empno) = mgr; 表示進行層級查詢
level 自動遞增