Python学习日记(三十七) Mysql数据库篇 五

pymsql的使用

初识pymysql模块

先在数据库中创建一个用户信息表,里面包含用户的ID、用户名、密码

create table userinfo(
    uid int not null auto_increment primary key,
    username varchar(32),
    pwd varchar(32)
)engine = innodb default charset=utf8;

增加一个用户的信息:

insert into userinfo(username,pwd) values('jxson','a123');

用pymysql模块从数据库拿到用户信息模拟登陆效果:

import pymysql
user = input('username:')                                                               #输入用户的名字
pwd = input('password:')                                                                #输入用户的密码
conn = pymysql.connect(host ='localhost',user = 'root',password = '',database = 'db1')  #连接数据库
cursor = conn.cursor()                                                                  #cursor是一个游标 去帮我们获取数据
sql_search = "select * from userinfo where username='%s' and pwd='%s'" %(user,pwd,)     #SQL语句
cursor.execute(sql_search)                                                              #执行SQL语句
get_one = cursor.fetchone()                                                             #拿一组数据
cursor.close()                                                                          #关闭游标
conn.close()                                                                            #关闭连接
if get_one:                                                                             #判断是否有拿到数据
    print("登陆成功!")
    print(get_one)
else:
    print("登陆失败!")

执行结果:

username:jxson
password:a123
登陆成功!
(1, 'jxson', 'a123')

防止SQL注入的改进方法

1.

sql_search = "select * from userinfo where username=%s and pwd=%s"
cursor.execute(sql_search,user,pwd)  

2.列表的表示方式

sql_search = "select * from userinfo where username=%s and pwd=%s"
cursor.execute(sql_search,[user,pwd])

3.字典的表示方式

sql_search = "select * from userinfo where username=%(u)s and pwd=%(p)s"
cursor.execute(sql_search,{'u' : user,'p' : pwd})

 增、删、改、查

增、删、改:

增、删、改都需要commit(),以增为举例

增加单个

import pymysql
conn = pymysql.connect(host ='localhost',user = 'root',password = '',database = 'db1')
cursor = conn.cursor()
sql_insert = "insert into userinfo(username,pwd) values('abc','666')"
cursor.execute(sql_insert)
conn.commit()
cursor.close()
conn.close()

增加多个:

import pymysql
conn = pymysql.connect(host ='localhost',user = 'root',password = '',database = 'db1')
cursor = conn.cursor()
sql_insert = "insert into userinfo(username,pwd) values(%s,%s)"
cursor.executemany(sql_insert,[('hylisang','a123'),('HSI15','47a8'),('asw2','')])
conn.commit()
cursor.close()
conn.close()

output:

查:

1.fetchone()

import pymysql
conn = pymysql.connect(host ='localhost',user = 'root',password = '',database = 'db1')
cursor = conn.cursor()
sql = "select * from userinfo"
cursor.execute(sql)
result1 = cursor.fetchone()
print(result1)
result2 = cursor.fetchone()
print(result2)
cursor.close()
conn.close()

执行结果:

(1, 'jxson', 'a123')
(6, 'abc', '')

2.fetchmany(n),一次取n条数据

import pymysql
conn = pymysql.connect(host ='localhost',user = 'root',password = '',database = 'db1')
cursor = conn.cursor()
sql = "select * from userinfo"
cursor.execute(sql)
result1 = cursor.fetchmany(3)
print(result1)
cursor.close()
conn.close()

执行结果:

((1, 'jxson', 'a123'), (6, 'abc', ''), (7, 'hylisang', 'a123'))

3.fetchall(),一次取全部SQL语句查到的数据

import pymysql
conn = pymysql.connect(host ='localhost',user = 'root',password = '',database = 'db1')
cursor = conn.cursor()
sql = "select * from userinfo"
cursor.execute(sql)
result1 = cursor.fetchall()
print(result1)
cursor.close()
conn.close()

执行结果:

((1, 'jxson', 'a123'), (6, 'abc', ''), (7, 'hylisang', 'a123'), (8, 'HSI15', '47a8'), (9, 'asw2', ''))

把结果转化为字典的格式:

import pymysql
conn = pymysql.connect(host ='localhost',user = 'root',password = '',database = 'db1')
cursor = conn.cursor(cursor=pymysql.cursors.DictCursor)
sql = "select * from userinfo"
cursor.execute(sql)
result1 = cursor.fetchall()
print(result1)
cursor.close()
conn.close()

执行结果:

[{'uid': 1, 'username': 'jxson', 'pwd': 'a123'}, {'uid': 6, 'username': 'abc', 'pwd': ''}, {'uid': 7, 'username': 'hylisang', 'pwd': 'a123'},
 {'uid': 8, 'username': 'HSI15', 'pwd': '47a8'}, {'uid': 9, 'username': 'asw2', 'pwd': ''}]

4.控制游标来获取数据

cursor.scroll(1,mode='relative')    　　　　　　　　　　　　　　　　　　　　　　　　　　　　#根据当前位置相对位移
cursor.scroll(2,mode='absolute')    　　　　　　　　　　　　　　　　　　　　　　　　　　　　#绝对位置移动

查看新插入数据的自增ID

如果添加多笔数据再去查询,那查到的ID是最后一条

import pymysql
conn = pymysql.connect(host ='localhost',user = 'root',password = '',database = 'db1')
cursor = conn.cursor(cursor=pymysql.cursors.DictCursor)
sql_insert = "insert into userinfo(username,pwd) values('abc','666')"
cursor.execute(sql_insert)
print(cursor.lastrowid)
conn.commit()
cursor.close()
conn.close()