echo_pn

select ename,sal from emp where empno in (select empno from (select empno,sal from emp order by sal desc )t where rownum<4); declare v_name varchar2(10); v_sal number(5); cur...

 oracle中的组函数包括：  AVG   COUNT  MAX  MIN  SUM  VARIANCE方差    STDDEV标准差，其中 MIX MAX用于任何数据类型，AVG SUM VARIANCE STDDEV函数只能用于数据。 select MIN(cls.clsname) name, MIN(cls.stuname) stuname, cls.clsno no from stu...