1.简单查询

select * from info;

select Code as '代号',name as '姓名' from info;

2.条件查询

select * from car where code = 'c002';

select * from car where brand ='b001' and power = 130; #或用or

3.模糊查询

select * from car where name like '%奥迪%';  %代表任意多个字符包括0个 _代表一个字符

4.排序查询

asc:顺序排序（默认）  desc：倒序排序

select * from car order by brand, powers desc; asc升序默认可以不写

5.离散查询

in() :查询符合括号里面的数据    not in() :除了括号里面的数据其他都查询

select * from car where code in('coo1','c003','c005','c007');

select * from car where code not in('coo1','c003','c005','c007');

6.统计查询（聚合函数）

select count(code) from car;　　查询数据条数也可以count(*)这么写，性能低

select sum(price) from car;　　求和

select max(code) from car;　　最大　　

select min(brand) from car;　　最小

select avg(price) from car;　　平均

7.分组查询

select brand,count(*),Brand from Car group by Brand 　　#把brand列的相同值组合起来，并这一条数据对该列或或其他列进行操作例如求平均值

select Brand from Car group by Brand having count(*)>3 #分组之后根据条件查询使用having 不使用where