5 DQL

select ename from emp where ename like '_C%';
select * from emp where sal in(800,1600,950);
select * from emp where mgr is null;
select * from emp where sal between 2000 and 3000;
select * from emp where (sal>500 or job='manager') and (ename like 'J%');

select avg(sal),max(sal),deptno,job from emp group by deptno,job order by deptno;/***group by要配合聚合函数,如max(),min(),avg(),count(),sum()***/
select avg(sal) deptno from emp group by deptno having avg(sal)>2000;/***having过滤分组结果***/

select * from emp order by deptno,sal desc;
select (sal+nvl(comm,0))*13 年薪 from emp order by 年薪;
select * from emp order by 1;
select *from emp order by sal+comm;
select *from emp order by comm nulls first;