一、查询所有数据
select * from car
二、查询指定列
select code , price from car
三、修改查询出的列名
select code as '代号' , name as '车牌' from car
四、条件查询
单条件查询
select * from car where code='c002'
多条件查询（用or或者and链接）
select * from car where code='c002'or price='37.16'
select * from car where code='c002' and price='67.49'
五、模糊查询（关键字查询）
%关键字，关键字前面有n个字符；关键字%，关键字后面有n个字符
_关键字，关键字前面有一个字符；关键字_，关键字后面有一个字符
select * from car where name like '奥迪%'
六、排序查询
desc降序 asc升序。
默认为升序
select * from car order by price desc
根据价格降序排列
select *from car order by price desc, oil desc
先根据price降序排列，有重复的 在根据oil降序排列
七、去重查询
distinct去重
select distinct brand from car
八、分页查询
select * from car limit 5, 5 #跳5条不包括5，取5条
九、统计查询（聚合查询）
数据条数
select count(*) from car
select count(code) from car
select max(列名) from 表名 #取最大值 select min（列名） from 表名#取最小值 select avg （列名）from 表名#取平均值
十、分组查询
select * from car group by brand
select brand ,count(*)from car group by brand
select brand from car group by brand having count(*)>=3 #有having前面必须有group by 有group by 后面可以没有having
十一、范围查询 in 和 not in 相反 一个是是这些数的 一个是不是这些数的
select * from car where price between 40 and 60
十二、离散查询
select * from car where price in (10,20,30,40,50,60)
select * from car where price not in (10,20,30,40,50,60)
