查询：
1.简单查询
select * from Info --查所有数据
select Code,Name from Info --查指定列的数据
select Code as '代号',Name as '姓名' from Info --给列指定别名
2.条件查询
select * from Info where Code='p001'
select * from Info where Sex='true' and Nation='n001' --多条件并的关系
select * from Info where Sex='true' or Nation='n001' --多条件或的关系
3.范围查询
select * from Car where Price>40 and Price<50
select * from Car where Price between 40 and 50
4.离散查询
select * from Car where Code in ('c001','c005','c010','c015')
select * from Car where Code not in ('c001','c005','c010','c015')
5.模糊查询
select * from Car where Name like '%宝马%' --查包含宝马的
select * from Car where Name like '宝马%' --查以宝马开头的
select * from Car where Name like '%宝马' --查以宝马结尾的
select * from Car where Name like '宝马' --查等于宝马的
select * from Car where Name like '__E%' --查第三个字符是E的
% 代表是任意多个字符
_ 代表是一个字符
6.排序查询
select * from Car order by Price asc --以价格升序排列
select * from Car order by Price desc --以价格降序排列
select * from Car order by Oil desc,Price asc --以两个字段排序，前面的是主条件后面的是次要条件
7.分页查询
select top 5 * from Car
select top 5 * from Car where Code not in (select top 5 Code from Car)
当前页:page = 2; 每页显示：row = *，每页显示*条
select top row * from Car where Code not in (select top (page-1)*row Code from Car)
8.去重查询
select distinct Brand from Car
9.分组查询
select Brand from Car group by Brand having count(*)>2
10.聚合函数(统计查询)
select count(*) from Car --查询所有数据条数
select count(Code) from Car --查询所有数据条数
select sum(Price) from Car --求和
select avg(Price) from Car --求平均
select max(Price) from Car --求最大值
select min(Price) from Car --求最小值
