Python操作MySQL数据库的示例代码

1. MySQL Connector

1.1 创建连接

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","port":"3306",
  "user":"root","password":"password",
  "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, 'SALESMAN', Decimal('1250.00'))
  (7566, 'MANAGER', Decimal('2975.00'))
  (7654, 'SALESMAN', Decimal('1250.00'))
  (7698, 'MANAGER', Decimal('2850.00'))
  (7782, 'MANAGER', Decimal('2450.00'))
  (7788, 'ANALYST', Decimal('3000.00'))
  (7839, 'PRESIDENT', Decimal('5000.00'))
  (7844, 'SALESMAN', Decimal('1500.00'))
  (7900, 'CLERK', Decimal('950.00'))
  (7902, 'ANALYST', Decimal('3000.00'))
  (7934, 'CLERK', Decimal('1300.00'))

1.3 SQL注入攻击

1. username=1 OR 1=1 password=1 OR 1=1

2. 在使用字符串直接拼接时OR之前不管对错，与OR结合都为true

3. 解决方法——预编译（也可以提高速度）

1.4 事务管理和异常处理

sql连接和使用异常处理异常

import mysql.connector
try:
  con=mysql.connector.connect(
    host="localhost",port="3306",
    user="root",password="password",
    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 删除数据

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() 反复执行一条SQL语句

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 = "INSERT INTO t_dept(deptno,dname,loc) VALUES(％s,％s,％s);"
  date=[[70,"SALES","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. 数据库连接池

1. 数据库的连接是昂贵的，一个连接要经过TCP三次握手，四次挥手，而且一台计算机的最大线程数也是有限的

2. 数据库连接池技术就是先创建好连接，再直接拿出来使用

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 = "INSERT INTO t_dept(deptno,dname,loc) VALUES(％s,％s,％s);"
  cursor.execute(sql, (70, "SALES", "HUBAI"))
  con.commit()
except Exception as e:
  if "con" in dir():
    con.rollback()
  print(e)
# do not need to close con

来源：https://www.cnblogs.com/zwhy8/archive/2020/07/13/13293335.html