Python操作MySQL資料庫的示例程式碼_資料庫

1. Mysql Connector

1.1 建立連線

import mysql.connector
 config={
   "host":"localhost","port":"3306","user":"root","password":"password","database":"demo"
 }
 con=mysql.connector.connect(**config)
 import mysql.connector
 config={
   "host":"localhost","database":"demo"
 }
 con=mysql.connector.connect(**config)

1.2 Cursor

import mysql.connector
 con=mysql.connector.connect(
   host="localhost",port="3306",user="root",password="password",database="demo"
 )
 cursor=con.cursor()
 sql="SELECT empno,job,sal FROM t_bonus;"
 cursor.execute(sql)
 print(type(cursor))
 for i in cursor:
   print(i)
 con.close()
 
 Result:
   <class 'mysql.connector.cursor_cext.CMySQLCursor'>
   (7369,'CLERK',Decimal('8000.00'))
   (7499,'SALESMAN',Decimal('1600.00'))
   (7521,Decimal('1250.00'))
   (7566,'MANAGER',Decimal('2975.00'))
   (7654,Decimal('1250.00'))
   (7698,Decimal('2850.00'))
   (7782,Decimal('2450.00'))
   (7788,'ANALYST',Decimal('3000.00'))
   (7839,'PRESIDENT',Decimal('5000.00'))
   (7844,Decimal('1500.00'))
   (7900,Decimal('950.00'))
   (7902,Decimal('3000.00'))
   (7934,Decimal('1300.00'))

1.3 SQL注入攻擊

username=1 OR 1=1 password=1 OR 1=1
在使用字串直接拼接時OR之前不管對錯，與OR結合都為true
解決方法——預編譯（也可以提高速度）

1.4 事務管理和異常處理

sql連線和使用異常處理異常

import mysql.connector
 try:
   con=mysql.connector.connect(
     host="localhost",database="demo"
   )
   con.start_transaction()
   cursor=con.cursor()
   sql="INSERT INTO t_dept(deptno,dname,loc) VALUES(%s,%s,%s);"
   cursor.execute(sql,(60,"SALES","HUBAI"))
   con.commit()
 except Exception as e:
   if "con" in dir():
     con.rollback()
   print(e)
 finally:
   if "con" in dir():
     con.close()

1.5 刪除資料

import mysql.connector,mysql.connector.pooling
 config={
   "host": "localhost","port": "3306","user": "root","password": "password","database": "demo"
 }
 try:
   pool=mysql.connector.pooling.MySQLConnectionPool(**config,pool_size=5)
   con=pool.get_connection()
   con.start_transaction()
   cursor = con.cursor()
   sql = "DELETE FROM t_dept WHERE deptno=%s"
   cursor.execute(sql,(70,))
   con.commit()
 except Exception as e:
   if "con" in dir():
     con.rollback()
   print(e)
 # do not need to close con

executemany() 反覆執行一條SQL語句

import mysql.connector,pool_size=5)
   con=pool.get_connection()
   con.start_transaction()
   cursor = con.cursor()
   sql = "INSERT INTO t_dept(deptno,%s);"
   date=[[70,"BEIJING"],[80,"ACTOR","SHANGHAI"]]
   cursor.executemany(sql,date)
   con.commit()
 except Exception as e:
   if "con" in dir():
     con.rollback()
   print(e)
 # do not need to close con

2. 資料庫連線池

資料庫的連線是昂貴的，一個連線要經過TCP三次握手，四次揮手，而且一臺計算機的最大執行緒數也是有限的
資料庫連線池技術就是先建立好連線，再直接拿出來使用

import mysql.connector,"HUBAI"))
   con.commit()
 except Exception as e:
   if "con" in dir():
     con.rollback()
   print(e)
 # do not need to close con

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Python操作MySQL資料庫的示例程式碼

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