复习mysql

Posted 2020-11-17 yangli0504

1.   pymysql 的安装

pip3 install pymysql

2.  pymysql的基本语法

mport pymysql

conn = pymysql.connect(

                                   host="127.0.0.1",

                                   port=3306,

                                   user="root",

                                   password="123",

                                   database="day62",

                                   charset="utf8"，

        autocommit=True,

                       )

cursor = conn.cursor()

           cursor.execute("select * from user;")

                  ret = cursor.fetchall() # fetchone, fetchmany

# conn.commit()

 

cursor.close()

conn.close()

 

3  pymsql：execute（）之sql注入

原因： 符号--会注释掉它之后的sql

 

例如： 在一条sql语句中如果遇到select * from t1 where id > 3 -- and name=‘egon‘;则--之后的条件被注释掉了

#1、sql注入之：用户存在，绕过密码

egon‘ -- 任意字符

#2、sql注入之：用户不存在，绕过用户与密码

xxx‘ or 1=1 -- 任意字符

 

解决方案：不自行进行sql语句拼接；execute帮我们做字符串拼接，我们无需且一定不能再为%s加引号了

sql="select * from userinfo where name=%s and password=%s" #！！！

res=cursor.execute(sql,[user,pwd])

 

4 单例简版orm（youku版）

 

Mysql_singleton.py

import pymysql

 

class Mysql:

   __instance=None 

   def __init__(self):

       self.conn=pymysql.connect(

           host=‘127.0.0.1‘,

           port=3306,

           user=‘root‘,

           password=‘123‘,

           charset=‘utf8‘,

           database=‘youku‘,

           autocommit=True

       )

       self.cursor=self.conn.cursor(cursor=pymysql.cursors.DictCursor)

 

   def close_db(self):

       self.cursor.close()

       self.conn.close()

 

   def select(self, sql, args=None):

       self.cursor.execute(sql, args)

       return self.cursor.fetchall()

 

   def execute(self, sql, args):

       try:

           self.cursor.execute(sql, args)

           affected = self.cursor.rowcount

       except BaseException as e:

           print(e)

       return affected

    

   @classmethod

   def singleton(cls):

       if not cls.__instance:

           cls.__instense=cls()

       return  cls.__instance

 

fuckorm.py

from orm import Mysql_singleton

 

class Fileld:

   def __init__(self,name,column_type,primary_key,default):

       self.name=name

       self.column_type=column_type

       self.primary_key= primary_key

       self.default=default

 

class StringFileld(Fileld):

   def __init__(self,name=None,column_type=‘varchar(200)‘,primary_key=False,default=None):

       super().__init__(name,column_type,primary_key,default)

 

class IntegerFileld(Fileld):

   def __init__(self,name=None,column_type=‘int‘,primary_key=False,default=0):

       super().__init__(name,column_type,primary_key,default)

 

class ModlesMetaclass(type):

   def __new__(cls, name,bases,attrs):

 

       if name==‘Modles‘:

           return type.__new__(cls,name,bases,attrs)

       table_name=attrs.get(‘table_name‘,None)

       primary_key=None

       mappings=dict()

       for k,v in attrs.items():

           if isinstance(v,Fileld):#v 是不是Field的对象

                mappings[k]=v

                if v.primary_key:

                    #找到主键

                    if primary_key:

                        raise TypeError(‘主键重复：%s‘%k)

                    primary_key=k

       for k in mappings.keys():

           attrs.pop(k)

       if not primary_key:

           raise TypeError(‘没有主键‘)

       attrs[‘table_name‘]=table_name

       attrs[‘primary_key‘]=primary_key

       attrs[‘mappings‘]=mappings

       return type.__new__(cls,name,bases,attrs)

 

class Modles(dict,metaclass=ModlesMetaclass):

   def __init__(self,**kwargs):

       super().__init__(**kwargs)

 

   def __setattr__(self, key, value):

       self[key]=value

 

   def __getattr__(self, item):

       try:

         return self[item]

       except TypeError:

           raise (‘没有该属性‘)

 

   @classmethod

   def select_one(cls,**kwargs):

       key=list(kwargs.keys())[0]

       value=kwargs[key]

       sql=‘select * from %s where %s=?‘%(cls.table_name,key)

       sql=sql.replace(‘?‘,‘%s‘)

       ms=Mysql_singleton.Mysql().singleton()

       re=ms.select(sql,value)

       if re:

            u=cls(**re[0])

           return u

       else:

           return

 

   @classmethod

   def select_many(cls,**kwargs):

       ms = Mysql_singleton.Mysql().singleton()

       if kwargs:

           key=list(kwargs.keys())[0]

           value=kwargs[key]

           sql = ‘select * from %s where %s=?‘ % (cls.table_name, key)

           sql = sql.replace(‘?‘, ‘%s‘)

           re = ms.select(sql, value)

       else:

           sql = ‘select * from %s‘%(cls.table_name)

           re = ms.select(sql)

       if re:

           lis_obj=[cls(**r) for r in re]

           return lis_obj

       else:

           return

 

   def update(self):

       ms = Mysql_singleton.Mysql().singleton()

       filed=[]

       pr=None

       args=[]

       for k,v in self.mappings.items():

           if v.primary_key:

                pr=getattr(self,v.name,None)

           else:

                filed.append(v.name + ‘=?‘)

               args.append(getattr(self,v.name,v.default))

       sql=‘update %s set %s where %s =%s‘%(self.table_name,‘,‘.join(filed),self.primary_key,pr)

       sql=sql.replace(‘?‘,‘%s‘)

       ms.execute(sql,args)

   def save(self):

       ms = Mysql_singleton.Mysql().singleton()

       filed=[]

       values=[]

       args=[]

       for k,v in self.mappings.items():

           if not v.primary_key:

                filed.append(v.name)

                values.append(‘?‘)

               args.append(getattr(self,v.name,v.default))

       sql =‘insert into %s (%s) VALUES (%s)‘%(self.table_name,‘,‘.join(filed),‘,‘.join(values))

       sql= sql.replace(‘?‘,‘%s‘)

       ms.execute(sql,args)