一、准备数据
1、创建数据表
-- 创建 "京东" 数据库createdatabasejdcharset=utf8;-- 使用 "京东" 数据库usejd;-- 创建一个商品goods数据表createtablegoods(idintunsignedprimarykeyauto_incrementnotnull,namevarchar(150)notnull, cate_namevarchar(40)notnull, brand_namevarchar(40)notnull, pricedecimal(10,3)notnulldefault0, is_showbitnotnulldefault1, is_saleoffbitnotnulldefault0);
2、插入数据
-- 向goods表中插入数据insertintogoodsvalues(0,'r510vc 15.6英寸笔记本','笔记本','华硕','3399',default,default);insertintogoodsvalues(0,'y400n 14.0英寸笔记本电脑','笔记本','联想','4999',default,default);insertintogoodsvalues(0,'g150th 15.6英寸游戏本','游戏本','雷神','8499',default,default);insertintogoodsvalues(0,'x550cc 15.6英寸笔记本','笔记本','华硕','2799',default,default);insertintogoodsvalues(0,'x240 超极本','超级本','联想','4880',default,default);insertintogoodsvalues(0,'u330p 13.3英寸超极本','超级本','联想','4299',default,default);insertintogoodsvalues(0,'svp13226scb 触控超极本','超级本','索尼','7999',default,default);insertintogoodsvalues(0,'ipad mini 7.9英寸平板电脑','平板电脑','苹果','1998',default,default);insertintogoodsvalues(0,'ipad air 9.7英寸平板电脑','平板电脑','苹果','3388',default,default);insertintogoodsvalues(0,'ipad mini 配备 retina 显示屏','平板电脑','苹果','2788',default,default);insertintogoodsvalues(0,'ideacentre c340 20英寸一体电脑 ','台式机','联想','3499',default,default);insertintogoodsvalues(0,'vostro 3800-r1206 台式电脑','台式机','戴尔','2899',default,default);insertintogoodsvalues(0,'imac me086ch/a 21.5英寸一体电脑','台式机','苹果','9188',default,default);insertintogoodsvalues(0,'at7-7414lp 台式电脑 linux ）','台式机','宏碁','3699',default,default);insertintogoodsvalues(0,'z220sff f4f06pa工作站','服务器/工作站','惠普','4288',default,default);insertintogoodsvalues(0,'poweredge ii服务器','服务器/工作站','戴尔','5388',default,default);insertintogoodsvalues(0,'mac pro专业级台式电脑','服务器/工作站','苹果','28888',default,default);insertintogoodsvalues(0,'hmz-t3w 头戴显示设备','笔记本配件','索尼','6999',default,default);insertintogoodsvalues(0,'商务双肩背包','笔记本配件','索尼','99',default,default);insertintogoodsvalues(0,'x3250 m4机架式服务器','服务器/工作站','ibm','6888',default,default);insertintogoodsvalues(0,'商务双肩背包','笔记本配件','索尼','99',default,default);
-- 查询类型cate_name为'超级本的商品
select name as 商品名称,priceas 商品价格from goodswhere cate_name ='超级本';
-- 显示商品的种类
select distinct cate_namefrom goods; -- 去重
select cate_namefrom goodsgroup by cate_name;-- 分组
-- 查询每个种类的商品名称
select cate_name,group_concat(name)from goodsgroup by cate_name;
-- 求所有电脑产品的平均价格，并且保留两位小数
select round(avg(price),2)from goods;
-- 显示每种商品的平均价格
select cate_name,avg(price)from goodsgroup by cate_name;
-- 查询每种类型的商品中最贵、最便宜、平均价、数量
select cate_name,max(price),min(price),avg(price),count(*)from goodsgroup by cate_name;
-- 查询所有价格大于平均价格的商品，并且按价格降序排序
select * from goodswhere price>(select avg(price)from goods)order by pricedesc;
-- 查询每种类型中最贵的电脑信息
select cate_name,max(price)from goodsgroup by cate_name;
select * from goods;
-- 相当于两句结合起来
select * from goods
inner join
(
select
cate_name,
max(price)as max_price,
min(price)as min_price,
avg(price)as avg_price,
count(*)from goodsgroup by cate_name
)as goods_new_info
on goods.cate_name=goods_new_info.cate_nameand goods.price=goods_new_info.max_price;
select * from (select cate_name,max(price)as max_pricefrom goodsgroup by cate_name)as g_new
left join goodsas g
on g_new.cate_name=g.cate_nameand g_new.max_price=g.priceorder by g_new.cate_name;
insert into goodsvalues(0,'东哥牌电脑','笔记本','老王','4999',default,default);
-- 创建商品分类表
create table if not exists goods_cates(
id int unsigned primary key auto_increment,
name varchar(40)not null
);
-- 查询goods商品的种类
select cate_namefrom goodsgroup by cate_name;
insert into goods_cates (name)select cate_namefrom goodsgroup by cate_name;
update goodsas ginner join goods_catesas con g.cate_name=c.name set g.cate_name=c.id;
insert into goods_cates(name)values ('路由器'),('交换机'),('网卡');
insert into goods (name,cate_id,brand_id,price)
values('LaserJet Pro P1606dn 黑白激光打印机', 12, 4,'1849');
alter table goods
change cate_namecate_id int unsigned not null;
alter table goodsadd foreign key (cate_id)references goods_cates(id);-- 外键关联
delete from goodswhere id=23;
-- 创建商品品牌表
create table if not exists goods_brands(
id int unsigned primary key auto_increment,
name varchar(40)not null
);
select brand_namefrom goodsgroup by brand_name;
insert into goods_brands (name)select brand_namefrom goodsgroup by brand_name;
update goodsas ginner join goods_brandsas bon g.brand_name=b.name set g.brand_name=b.id;
alter table goods
change brand_namebrand_id int unsigned not null;
alter table goodsadd foreign key (brand_id)references goods_brands(id);-- 外键关联
insert into goods (name,cate_id,brand_id,price)
values('LaserJet Pro P1606dn 黑白激光打印机', 2, 100,'1849');
-- 创建品牌表
create table goods_brands (
id int unsigned primary key auto_increment,
name varchar(40)not null)select brand_nameas name from goodsgroup by brand_name;
update goodsas ginner join goods_brandsas bon g.brand_name=b.name set g.brand_name=b.id;
alter table goods
change brand_namebrand_id int unsigned not null;
alter table goodsadd foreign key (brand_id)references goods_brands(id);
-- 取消外键
alter table goodsdrop foreign key goods_ibfk_1;
alter table goodsdrop foreign key goods_ibfk_2;
# 在python3中使用 数据库
# python2 import MySQLdb
import pymysql
'''
'''
from pymysqlimport connect
# 创建connection连接
conn = connect(host='localhost',port=3306,database='wn',user='root',password='root',charset='utf8')
# 获取cursor对象
cursor = conn.cursor()
count = cursor.execute("select * from goods;")
print('查询到%d条数据'%count)
# print(cursor.fetchone())
# print(cursor.fetchone())
# print(cursor.fetchone())
# print(cursor.fetchone())
#
# print(cursor.fetchmany())# 取一条
# print(cursor.fetchmany(3))# 传几条取几条
#
# print(cursor.fetchall()) #取所有
line_content = cursor.fetchone()
print(line_content)
print(line_content[0])
print(line_content[1])
print(line_content[2])
for tempin line_content:
print(temp)
lines = cursor.fetchmany(5)
for tempin lines:
print(temp)
# 关闭cursor对象
cursor.close()
conn.close()
# print(cursor.fetchone(),'--------->')
# count = cursor.execute("select * from goods;")
# 数据库关闭之后不能再调用代码