帮忙看看为什么两列的数据不一样的,select e.ename,e2.ename from emp e join emp e2 on
SQL> select e.ename,e2.ename from emp e join emp e2 on(e.mgr=e2.empno);
ENAME ENAME
---------- ----------
FORD JONES
SCOTT JONES
TURNER BLAKE
ALLEN BLAKE
WARD BLAKE
JAMES BLAKE
MARTIN BLAKE
MILLER CLARK
ADAMS SCOTT
BLAKE KING
JONES KING
CLARK KING
SMITH FORD
13 rows selected
SQL> select e.ename,e2.ename from emp e join emp e2 on(e.empno=e2.mgr);
ENAME ENAME
---------- ----------
JONES FORD
JONES SCOTT
BLAKE TURNER
BLAKE ALLEN
BLAKE WARD
BLAKE JAMES
BLAKE MARTIN
CLARK MILLER
SCOTT ADAMS
KING BLAKE
KING JONES
KING CLARK
FORD SMITH
13 rows selected
各位大哥帮忙看看为什么两列的数据会反过来的,为什么等值式反过来会这样
ENAME ENAME
---------- ----------
FORD JONES
SCOTT JONES
TURNER BLAKE
ALLEN BLAKE
WARD BLAKE
JAMES BLAKE
MARTIN BLAKE
MILLER CLARK
ADAMS SCOTT
BLAKE KING
JONES KING
CLARK KING
SMITH FORD
13 rows selected
SQL> select e.ename,e2.ename from emp e join emp e2 on(e.empno=e2.mgr);
ENAME ENAME
---------- ----------
JONES FORD
JONES SCOTT
BLAKE TURNER
BLAKE ALLEN
BLAKE WARD
BLAKE JAMES
BLAKE MARTIN
CLARK MILLER
SCOTT ADAMS
KING BLAKE
KING JONES
KING CLARK
FORD SMITH
13 rows selected
各位大哥帮忙看看为什么两列的数据会反过来的,为什么等值式反过来会这样
作者: Eason_Huang 发布时间: 2011-06-14
SQL code
select e.ename,e2.ename from emp e join emp e2 on(e.mgr=e2.empno) select e.ename,e2.ename from emp e join emp e2 on(e.empno=e2.mgr) ---因为你条件是反过来的,第2句中的e相当于第一句的e2 ---所以第2句中的e.ename相当于第一句中的e2.ename,e2.ename相当于第一句的e.ename
作者: X_0 发布时间: 2011-06-14