-- 創(chuàng)建 "京東" 數(shù)據(jù)庫 create database jing_dong charset=utf8; -- 使用 "京東" 數(shù)據(jù)庫 use jing_dong; -- 創(chuàng)建一個(gè)商品goods數(shù)據(jù)表 create table goods( id int unsigned primary key auto_increment not null, name varchar(150) not null, cate_name varchar(40) not null, brand_name varchar(40) not null, price decimal(10,3) not null default 0, is_show bit not null default 1, is_saleoff bit not null default 0 );
-- 向goods表中插入數(shù)據(jù) insert into goods values(0,'r510vc 15.6英寸筆記本','筆記本','華碩','3399',default,default); insert into goods values(0,'y400n 14.0英寸筆記本電腦','筆記本','聯(lián)想','4999',default,default); insert into goods values(0,'g150th 15.6英寸游戲本','游戲本','雷神','8499',default,default); insert into goods values(0,'x550cc 15.6英寸筆記本','筆記本','華碩','2799',default,default); insert into goods values(0,'x240 超極本','超級(jí)本','聯(lián)想','4880',default,default); insert into goods values(0,'u330p 13.3英寸超極本','超級(jí)本','聯(lián)想','4299',default,default); insert into goods values(0,'svp13226scb 觸控超極本','超級(jí)本','索尼','7999',default,default); insert into goods values(0,'ipad mini 7.9英寸平板電腦','平板電腦','蘋果','1998',default,default); insert into goods values(0,'ipad air 9.7英寸平板電腦','平板電腦','蘋果','3388',default,default); insert into goods values(0,'ipad mini 配備 retina 顯示屏','平板電腦','蘋果','2788',default,default); insert into goods values(0,'ideacentre c340 20英寸一體電腦 ','臺(tái)式機(jī)','聯(lián)想','3499',default,default); insert into goods values(0,'vostro 3800-r1206 臺(tái)式電腦','臺(tái)式機(jī)','戴爾','2899',default,default); insert into goods values(0,'imac me086ch/a 21.5英寸一體電腦','臺(tái)式機(jī)','蘋果','9188',default,default); insert into goods values(0,'at7-7414lp 臺(tái)式電腦 linux ）','臺(tái)式機(jī)','宏碁','3699',default,default); insert into goods values(0,'z220sff f4f06pa工作站','服務(wù)器/工作站','惠普','4288',default,default); insert into goods values(0,'poweredge ii服務(wù)器','服務(wù)器/工作站','戴爾','5388',default,default); insert into goods values(0,'mac pro專業(yè)級(jí)臺(tái)式電腦','服務(wù)器/工作站','蘋果','28888',default,default); insert into goods values(0,'hmz-t3w 頭戴顯示設(shè)備','筆記本配件','索尼','6999',default,default); insert into goods values(0,'商務(wù)雙肩背包','筆記本配件','索尼','99',default,default); insert into goods values(0,'x3250 m4機(jī)架式服務(wù)器','服務(wù)器/工作站','ibm','6888',default,default); insert into goods values(0,'商務(wù)雙肩背包','筆記本配件','索尼','99',default,default);
查詢類型cate_name為 '超極本' 的商品名稱、價(jià)格
select name,price from goods where cate_name = '超級(jí)本';
顯示商品的種類
select cate_name from goods group by cate_name;
求所有電腦產(chǎn)品的平均價(jià)格,并且保留兩位小數(shù)
select round(avg(price),2) as avg_price from goods;
顯示每種商品的平均價(jià)格
select cate_name,avg(price) from goods group by cate_name;
查詢每種類型的商品中 最貴、最便宜、平均價(jià)、數(shù)量
select cate_name,max(price),min(price),avg(price),count(*) from goods group by cate_name;
查詢所有價(jià)格大于平均價(jià)格的商品，并且按價(jià)格降序排序
select id,name,price from goods where price > (select round(avg(price),2) as avg_price from goods) order by price desc;
查詢每種類型中最貴的電腦信息
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 goods group by cate_name ) as goods_new_info on goods.cate_name=goods_new_info.cate_name and goods.price=goods_new_info.max_price;
-- 創(chuàng)建商品分類表 create table if not exists goods_cates( id int unsigned primary key auto_increment, name varchar(40) not null );
查詢goods表中商品的種類
select cate_name from goods group by cate_name;
將分組結(jié)果寫入到goods_cates數(shù)據(jù)表
insert into goods_cates (name) select cate_name from goods group by cate_name;
通過goods_cates數(shù)據(jù)表來更新goods表
update goods as g inner join goods_cates as c on g.cate_name=c.name set g.cate_name=c.id;
通過create...select來創(chuàng)建數(shù)據(jù)表并且同時(shí)寫入記錄,一步到位
-- select brand_name from goods group by brand_name; -- 在創(chuàng)建數(shù)據(jù)表的時(shí)候一起插入數(shù)據(jù) -- 注意: 需要對(duì)brand_name 用as起別名，否則name字段就沒有值 create table goods_brands ( id int unsigned primary key auto_increment, name varchar(40) not null) select brand_name as name from goods group by brand_name;
通過goods_brands數(shù)據(jù)表來更新goods數(shù)據(jù)表
update goods as g inner join goods_brands as b on g.brand_name=b.name set g.brand_name=b.id;
查看 goods 的數(shù)據(jù)表結(jié)構(gòu),會(huì)發(fā)現(xiàn) cate_name 和 brand_name對(duì)應(yīng)的類型為 varchar 但是存儲(chǔ)的都是數(shù)字
desc goods;
通過alter table語句修改表結(jié)構(gòu)
alter table goods change cate_name cate_id int unsigned not null, change brand_name brand_id int unsigned not null;
分別在 goods_cates 和 goods_brands表中插入記錄
insert into goods_cates(name) values ('路由器'),('交換機(jī)'),('網(wǎng)卡');
insert into goods_brands(name) values ('海爾'),('清華同方'),('神舟');
在 goods 數(shù)據(jù)表中寫入任意記錄
insert into goods (name,cate_id,brand_id,price)
values('LaserJet Pro P1606dn 黑白激光打印機(jī)', 12, 4,'1849');
查詢所有商品的詳細(xì)信息 (通過內(nèi)連接)
select g.id,g.name,c.name,b.name,g.price from goods as g inner join goods_cates as c on g.cate_id=c.id inner join goods_brands as b on g.brand_id=b.id;
查詢所有商品的詳細(xì)信息 (通過左連接)
select g.id,g.name,c.name,b.name,g.price from goods as g left join goods_cates as c on g.cate_id=c.id left join goods_brands as b on g.brand_id=b.id;
-- 給brand_id 添加外鍵約束成功 alter table goods add foreign key (brand_id) references goods_brands(id); -- 給cate_id 添加外鍵失敗 -- 會(huì)出現(xiàn)1452錯(cuò)誤 -- 錯(cuò)誤原因:已經(jīng)添加了一個(gè)不存在的cate_id值12,因此需要先刪除 alter table goods add foreign key (cate_id) references goods_cates(id);
create table goods( id int primary key auto_increment not null, name varchar(40) default '', price decimal(5,2), cate_id int unsigned, brand_id int unsigned, is_show bit default 1, is_saleoff bit default 0, foreign key(cate_id) references goods_cates(id), foreign key(brand_id) references goods_brands(id) );
如何取消外鍵約束
-- 需要先獲取外鍵約束名稱,該名稱系統(tǒng)會(huì)自動(dòng)生成,可以通過查看表創(chuàng)建語句來獲取名稱 show create table goods; -- 獲取名稱之后就可以根據(jù)名稱來刪除外鍵約束 alter table goods drop foreign key 外鍵名稱;
在實(shí)際開發(fā)中,很少會(huì)使用到外鍵約束,會(huì)極大的降低表更新的效率
create table goods_cates( id int unsigned primary key auto_increment not null, name varchar(40) not null );
create table goods_brands ( id int unsigned primary key auto_increment not null, name varchar(40) not null );
create table goods( id int unsigned primary key auto_increment not null, name varchar(40) default '', price decimal(5,2), cate_id int unsigned, brand_id int unsigned, is_show bit default 1, is_saleoff bit default 0, foreign key(cate_id) references goods_cates(id), foreign key(brand_id) references goods_brands(id) );
create table customer( id int unsigned auto_increment primary key not null, name varchar(30) not null, addr varchar(100), tel varchar(11) not null );
create table orders( id int unsigned auto_increment primary key not null, order_date_time datetime not null, customer_id int unsigned, foreign key(customer_id) references customer(id) );
create table order_detail( id int unsigned auto_increment primary key not null, order_id int unsigned not null, goods_id int unsigned not null, quantity tinyint unsigned not null, foreign key(order_id) references orders(id), foreign key(goods_id) references goods(id) );
在py文件中引入pymysql模塊
from pymysql import *
conn=connect(參數(shù)列表)
對(duì)象的方法
cs1=conn.cursor()
對(duì)象的方法
對(duì)象的屬性
from pymysql import *
def main():
# 創(chuàng)建Connection連接
conn = connect(host='localhost',port=3306,database='jing_dong',user='root',password='mysql',charset='utf8')
# 獲得Cursor對(duì)象
cs1 = conn.cursor()
# 執(zhí)行insert語句，并返回受影響的行數(shù)：添加一條數(shù)據(jù)
# 增加
count = cs1.execute('insert into goods_cates(name) values("硬盤")')
#打印受影響的行數(shù)
print(count)
count = cs1.execute('insert into goods_cates(name) values("光盤")')
print(count)
# # 更新
# count = cs1.execute('update goods_cates set name="機(jī)械硬盤" where name="硬盤"')
# # 刪除
# count = cs1.execute('delete from goods_cates where id=6')
# 提交之前的操作，如果之前已經(jīng)之執(zhí)行過多次的execute，那么就都進(jìn)行提交
conn.commit()
# 關(guān)閉Cursor對(duì)象
cs1.close()
# 關(guān)閉Connection對(duì)象
conn.close()
if __name__ == '__main__':
main()
from pymysql import *
def main():
# 創(chuàng)建Connection連接
conn = connect(host='localhost',port=3306,user='root',password='mysql',database='jing_dong',charset='utf8')
# 獲得Cursor對(duì)象
cs1 = conn.cursor()
# 執(zhí)行select語句，并返回受影響的行數(shù)：查詢一條數(shù)據(jù)
count = cs1.execute('select id,name from goods where id>=4')
# 打印受影響的行數(shù)
print("查詢到%d條數(shù)據(jù):" % count)
for i in range(count):
# 獲取查詢的結(jié)果
result = cs1.fetchone()
# 打印查詢的結(jié)果
print(result)
# 獲取查詢的結(jié)果
# 關(guān)閉Cursor對(duì)象
cs1.close()
conn.close()
if __name__ == '__main__':
main()
from pymysql import *
def main():
# 創(chuàng)建Connection連接
conn = connect(host='localhost',port=3306,user='root',password='mysql',database='jing_dong',charset='utf8')
# 獲得Cursor對(duì)象
cs1 = conn.cursor()
# 執(zhí)行select語句，并返回受影響的行數(shù)：查詢一條數(shù)據(jù)
count = cs1.execute('select id,name from goods where id>=4')
# 打印受影響的行數(shù)
print("查詢到%d條數(shù)據(jù):" % count)
# for i in range(count):
# # 獲取查詢的結(jié)果
# result = cs1.fetchone()
# # 打印查詢的結(jié)果
# print(result)
# # 獲取查詢的結(jié)果
result = cs1.fetchall()
print(result)
# 關(guān)閉Cursor對(duì)象
cs1.close()
conn.close()
if __name__ == '__main__':
main()
from pymysql import *
def main():
find_name = input("請(qǐng)輸入物品名稱：")
# 創(chuàng)建Connection連接
conn = connect(host='localhost',port=3306,user='root',password='mysql',database='jing_dong',charset='utf8')
# 獲得Cursor對(duì)象
cs1 = conn.cursor()
# # 非安全的方式
# # 輸入 " or 1=1 or " (雙引號(hào)也要輸入)
# sql = 'select * from goods where name="%s"' % find_name
# print("""sql===>%s====""" % sql)
# # 執(zhí)行select語句，并返回受影響的行數(shù)：查詢所有數(shù)據(jù)
# count = cs1.execute(sql)
# 安全的方式
# 構(gòu)造參數(shù)列表
params = [find_name]
# 執(zhí)行select語句，并返回受影響的行數(shù)：查詢所有數(shù)據(jù)
count = cs1.execute('select * from goods where name=%s', params)
# 注意：
# 如果要是有多個(gè)參數(shù)，需要進(jìn)行參數(shù)化
# 那么params = [數(shù)值1, 數(shù)值2....]，此時(shí)sql語句中有多個(gè)%s即可
# 打印受影響的行數(shù)
print(count)
# 獲取查詢的結(jié)果
# result = cs1.fetchone()
result = cs1.fetchall()
# 打印查詢的結(jié)果
print(result)
# 關(guān)閉Cursor對(duì)象
cs1.close()
# 關(guān)閉Connection對(duì)象
conn.close()
if __name__ == '__main__':
main()
以上就是MySQL和Python交互的示例的詳細(xì)內(nèi)容，更多關(guān)于MySQL和python交互的資料請(qǐng)關(guān)注腳本之家其它相關(guān)文章！
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