lombok

create database shop;NBSP //创建一个名为shop的数据库

use shop;NBSP //使用shop库

//建一张名为Product的表

//包含一个id字段，字段类型为int(整数)not null表示不允许为null， promary key表示该字段为主键，auto_increment表水

create table Product(id int not null primary key auto_increment);

//添加表结构语句 添加一个名为name的 类型为verchr(字符串，长度为100)的属性到product表中

alter table Product add column name varchar(100);

//删除表结构语句

alter table Product drop column name;

//查看product的表结构

desc Product;

//添加一条数据小括号里写我要添加那些字段，values后按照顺序写值

insert into Product (name,project,type) values("帽子"99"服饰");

//查询Product表中全部的数据

select * from Product;

//副除Product表中id为1的数据

//分组查询，统计有多少条

select type,count(*) from Product group by type;

//打八折,AS改名字

select name,price,price * 0.8 AS price2 from Product;

//大于300打八折

select name,price,price * 0.8 AS price2 from Product where price > 300;

//大于380打八折

select name,price,price * 0.8 AS price2 from Product where price <= 380 and type='衣服';

//求和

select sum(price) from Product;

//平均值

select avg(price) from Product;

//最大值

select max(price) from Product;

//最大值最小值

select max(price), min(price) from Product;

//删除Product表中id为1的数据

delet from Product where id=1;

//修改Product表中id为2的记录的name值为拖鞋

update Product set name="拖鞋"where id=2;

//条件查询

select * from Product where type="服饰";

//多个条件查询

select * from Product where type="服饰" and price >=100;

//只查询name,price

select name,price from Product;

//分组查询

select type from Product group by type;

//去重查询

select distinct type from Product;

//分组查询，统计有多少条

select type,count(*) from Product group by type;