简单Sql语句 having group By

select * from s;
select * from p;
select * from sp;

select * from emp;
alter table emp add(now char(20));
insert into emp values(7355,'huige','study',7233,sysdate,1500.00,200,20,'2014年6月8日');
select to_char(sysdate,'yyyy-mm-dd hh:mm;ss') from emp;
select to_char(sysdate,'yyyy "年" mm "月" dd "日"') from emp;
select to_date('2014-6-8','yyyy-mm-dd') from emp;
select to_char(1500.00,'009,999.99') from emp;--oracl必须用9来表示
commit();--提交
select to_number('100')from emp;

select avg(sal) 平均值 from emp;
select max(sal) 最大值 from emp;
select min(sal) 最小值 from emp;
select sum(sal) 总合 from emp;

select count(now)  from emp;--统计
select deptNo from emp group by deptNo;--查询部分编号 deptNo，按照deptNo来查找 即group by所跟的deptNo时，select后面就必须出现deptNo；---字段类必须出现
select deptNo ,sum(sal)from emp group by deptNo;--聚合函数不用出现

---having子句的应用
select deptNo,avg(sal) 平均值 from emp group by deptNo
having avg(sal)>2000 ; --having不能单独使用