假设我们有以下表格:
create table Employee(
2 EMPNO NUMBER(3),
3 ENAME VARCHAR2(15 BYTE),
4 HIREDATE DATE,
5 ORIG_SALARY NUMBER(6),
6 CURR_SALARY NUMBER(6),
7 REGION VARCHAR2(1 BYTE),
8 MANAGER_ID NUMBER(3)
9 )
并且
create table job (
2 EMPNO NUMBER(3),
3 jobtitle VARCHAR2(20 BYTE)
4 )
5 /
我对下面的查询语句很感兴趣
SELECT empno, manager_id, ename
2 FROM employee
3 START WITH empno = 1
4 CONNECT BY PRIOR empno = manager_id;
据我理解,这段代码从employee表中选择empno、manager_id和ename列,它从满足 empno=1
条件的行开始选择,但是我无法理解这一行代码的作用:
but could not understand what this line does:
CONNECT BY PRIOR empno = manager_id;
这是同一个意思吗:
where empno=manager_id?