查询语句

1.普通查询
select * from Info #查询所有内容

select Code,Name from Info #查询某几列

2.条件查询
select * from Info where Nation = 'n001' #条件查询

select * from Info where Nation = 'n001' and Sex = true #条件之间并的关系

select * from Info where Sex = false or Nation = 'n002' #条件之间或者的关系

3.模糊查询 关键字 like  %表示若干字符

select * from Chinastates where AreaName like '中%' #查询以“中”开头的

select * from Chinastates where AreaName like '%城%' #查询包含“城”的信息

select * from Chinastates where AreaName like '_城%' #查询“城”在第二个位置出现的数据

4.排序查询 关键字 order by   desc 降序 asc升序

select * from Car order by Code desc #desc 降序 asc升序

select * from Car order by Brand

select * from Car order by Brand , Powers #按照两个列排序

5.统计查询（聚合函数） 关键字 count max min sum

select count(Code) from Car #查询总条数

select max(Price) from Car #查询最大值

select min(Price) from Car #查询最小值

select avg(Price) from Car #查询平均值

select sum(Price) from Car #查询总和

6.分组查询  关键字 group by

select Brand,count(*) from Car group by Brand #根据系列分组查看每组的数据条数

select * from Car group by Brand having count(*)>2 #查询分组之后数据条数大于2的

7.分页查询 关键字 limit

select * from Car limit 5,5 #跳过几条数据取几条数据 （N-1）*5