mysql项目演练

create table goods(
id int unsigned primary key auto_increment not null,
name varchar(150) not null, -- 商品名称
cate varchar(40) not null, -- 商品形态
brand_name varchar(40) not null, -- 商品品牌
price decimal(10,3) not null default 0, -- 商品的价格
is_show bit not null default 1, -- 是否上架
is_saleoff bit not null default 0 -- 是否打折
);

insert into goods values(0,'r510vc 15.6英寸笔记本','笔记本','华硕','3399',default,default);
insert into goods values(0,'y400n 14.0英寸笔记本电脑','笔记本','联想','4999',default,default);
insert into goods values(0,'g150th 15.6英寸游戏本','游戏本','雷神','8499',default,default);
insert into goods values(0,'x550cc 15.6英寸笔记本','笔记本','华硕','2799',default,default);
insert into goods values(0,'x240 超极本','超级本','联想','4999',default,default);
insert into goods values(0,'u330p 13.3英寸超极本','超级本','联想','4299',default,default);
insert into goods values(0,'svp13226scb 触控超极本','超级本','索尼','7999',default,default);
insert into goods values(0,'ipad mini 7.9英寸平板电脑','平板电脑','苹果','1998',default,default);
insert into goods values(0,'ipad air 9.7英寸平板电脑','平板电脑','苹果','3388',default,default);
insert into goods values(0,'ipad mini 配备 retina 显示屏','平板电脑','苹果','2788',default,default);
insert into goods values(0,'ideacentre c340 20英寸一体电脑 ','台式机','联想','3499',default,default);
insert into goods values(0,'vostro 3800-r1206 台式电脑','台式机','戴尔','2899',default,default);
insert into goods values(0,'imac me086ch/a 21.5英寸一体电脑','台式机','苹果','9188',default,default);
insert into goods values(0,'at7-7414lp 台式电脑 linux ）','台式机','宏碁','3699',default,default);
insert into goods values(0,'z220sff f4f06pa工作站','服务器/工作站','惠普','4288',default,default);
insert into goods values(0,'poweredge ii服务器','服务器/工作站','戴尔','5388',default,default);
insert into goods values(0,'mac pro专业级台式电脑','服务器/工作站','苹果','28888',default,default);
insert into goods values(0,'hmz-t3w 头戴显示设备','笔记本配件','索尼','6999',default,default);
insert into goods values(0,'商务双肩背包','笔记本配件','索尼','99',default,default);
insert into goods values(0,'x3250 m4机架式服务器','服务器/工作站','ibm','6888',default,default);
insert into goods values(0,'hmz-t3w 头戴显示设备','笔记本配件','索尼','6999',default,default);
insert into goods values(0,'商务双肩背包','笔记本配件','索尼','99',default,default);

select * from goods;

select * from goods where price > (select avg(price) from goods) order by price desc;

select price from goods where cate = '超级本' ORDER BY price desc;

create table if not exists goods_cates(
cate_id int UNSIGNED primary key auto_increment,
cate_name varchar(40)
);

select DISTINCT cate from goods;

insert into goods_cates(cate_name) select DISTINCT cate from goods;

select cate_id from goods_cates;

update goods as g INNER JOIN goods_cates as c on g.cate=c.cate_name set g.cate=c.cate_id;

create table good_brands(
id int UNSIGNED PRIMARY KEY auto_increment not null,
brand_name varchar(40)
);

select * from good_brands;

select DISTINCT brand_name from goods;

insert into good_brands(brand_name) select DISTINCT brand_name from goods;

select brand_name from goods;

update goods as g INNER JOIN good_brands as b on g.brand_name = b.brand_name SET g.brand_name=b.id;

alter table goods change cate cate_id int UNSIGNED;

alter table goods change brand_name brand_id int UNSIGNED;

-- 将cate_id和id类型转换为int(11)

alter table goods_cates change cate_id cate_id int(11);

alter table good_brands change id id int(11);

-- 外键约束的创建和删除

alter table goods add foreign key(brand_id) references good_brands(id);

alter table goods add foreign key(cate_id) references goods_cates(cate_id);