random随机函数

SQL> select * from (select ename,job from emp order by dbms_random.value() ) where  rownum <5
  2  ;

ENAME	   JOB
---------- ---------
WARD	   SALESMAN
JAMES	   CLERK
BLAKE	   MANAGER
KING	   PRESIDENT

SQL> /

ENAME	   JOB
---------- ---------
TURNER	   SALESMAN
CLARK	   MANAGER
SMITH	   CLERK
WARD	   SALESMAN

SQL> /

ENAME	   JOB
---------- ---------
SCOTT	   ANALYST
KING	   PRESIDENT
SMITH	   CLERK
CLARK	   MANAGER

SQL> /

ENAME	   JOB
---------- ---------
SCOTT	   ANALYST
JAMES	   CLERK
JONES	   MANAGER
SMITH	   CLERK