- PRIOR ：之前的
- 从员工7876出发向上查看
select empno, ename, job, mgr
from emp
start with empno = 7876
connect by prior mgr = empno
- 从员工KING出发向下查看
select level, ename ||'work for' ||prior ename
from emp
start with ename='KING'
connect by prior empno = mgr
order by level
- lpad（列名，总长度，列名对应的值不足总长度的话，左边补充的字符）
- where ename<>'JONES' 不显示JONES
- connect by中加入ename<>'JONES'意思是不显示JONES之后的所有人
