6.3 数据库增删改查

Posted 2020-11-10 sun1987

添加表数据

 1 insert into car values(‘ ‘,‘  ‘,‘  ‘, ‘ ‘,‘ ‘);

2  insert  into car(字段1，字段2，....) values(值1，值2，.....);

3 insert into car set 字段1=值一，字段2=值2，...；

修改表数据

update car set 字段1= 值 where 字段2=值

删除表数据

delete from 表名 where 字段1 = 值

================简单查询===============

1最简单查询

select * from car;

2查询指定列

select name，oil，powers from car；

3 对查出的列名修改名字

select name as ‘ 车名’，oil as ‘油耗’，powers as ‘动力’ from car;

4 按条件查询

select name ，oil，powers from car where oil = 8.7；

5 多条件查询

select name， oil， powers from car where oil=8.7 or powers =160；

select name，oil， powers from car where oil = 8.7 and powers =160；

6 范围查询

select * from car where price>=40and price<=60;

select * from car where price between 40 and 60；

7离散查询

select * from car where powers = 130 or powers=150 or powers=170；

select *from car where powers in （130，150，170）；

 select * from car where powers not in (130,150,170）；

8模糊查询

select *from car where name like ‘ %宝马%’；

select * from car where name like “_宝马%";    _代表一个字符

9 排序查询  asc 升序  desc 降序  order 排队

select * from car order by oil asc;

select  * from car order by brand asc,price desc;

10去重复查询 distinct

select distinct brand from car；

11分页查询

select* from car limit 10，5；

n:m=5

limit (n-1)*m,m;

12 聚合函数查询

count(列名）sum(列名)    avg(列名)    max(列名)   min(列名)

select count(*) from car;

select sum(price) from car;

select avg(price) from car;

select max(price) from car;

select min(price) from car;