聚合函数
聚合函数：
1、max最大值 select max(price) from car where code='c024'
2、min最小值 select * from car where oil= (select min(price) from car)
3、avg平均值 select avg(price) as 平均价格 from car
4、sum求和 select sum (price) from car
5、count数量 select count (*) from car
起别名：
select avg(price) as 平均价格 from car
1.select * from car oil in (7.4,8.5,8.6)
2.select * from car oil not in (7.4,8.5,8.6)
3.select *from car where oil >=7 and oil <=8
4.select * from car where oil between 7 and 8
5.select *from car where oil >any(select oil from car where code='c024' or code ='c014')
6.select * from car where oil >all(select oil from car where code='c024' or code ='c014')