【语法14】Python-mysql-connector驱动

MySQL 是最流行的关系型数据库管理系统。

本章节我们为大家介绍使用 mysql-connector 来连接使用 MySQL， mysql-connector 是 MySQL 官方提供的驱动器。

我们可以使用 pip 命令来安装 mysql-connector：

python3 -m pip install mysql-connector

使用以下代码测试 mysql-connector 是否安装成功：

import mysql.connector

执行以上代码，如果没有产生错误，表明安装成功。

创建数据库连接

import mysql.connector

mydb = mysql.connector.connect(
  host="localhost",       # 数据库主机地址
  user="root",    # 数据库用户名
  passwd=""   # 数据库密码
)
 
print(mydb)

#创建数据库

import mysql.connector

mydb = mysql.connector.connect(
    host = 'localhost',
    user = 'root',
    passwd = '',
)

mycursor = mydb.cursor()

mycursor.execute("CREATE DATABASE test2_db")

mycursor.execute("SHOW DATABASES")

for x in mycursor:
    print(x)

('information_schema',)
('mysql',)
('performance_schema',)
('sys',)
('test1_db',)
('test2_db',)
('test_db',)

#或者我们可以直接连接数据库，如果数据库不存在，会输出错误信息

import mysql.connector

mydb = mysql.connector.connect(
    host = 'localhost',
    user = 'root',
    passwd = '',
    database = 'test_db'
)

创建数据表

# 创建数据表

import mysql.connector

mydb = mysql.connector.connect(
    host = 'localhost',
    user = 'root',
    passwd = '',
    database = 'test_db',
)

mycursor = mydb.cursor()

mycursor.execute("CREATE TABLE test(name VARCHAR(255),url VARCHAR(255))")

#显示数据表

import mysql.connector

mydb = mysql.connector.connect(
    host = 'localhost',
    user = 'root',
    passwd = '',
    database = 'test_db',
)

mycursor = mydb.cursor()

mycursor.execute("SHOW TABLES")

for x in mycursor:
    print(x)

('test',)

#设置主键

import mysql.connector

mydb = mysql.connector.connect(
    host = 'localhost',
    user = 'root',
    passwd = '',
    database = 'test_db',
)

mycursor = mydb.cursor()

mycursor.execute("ALTER TABLE test ADD COLUMN id INT AUTO_INCREMENT PRIMARY KEY")

插入数据

#插入一条记录
import mysql.connector

mydb = mysql.connector.connect(
    host = 'localhost',
    user = 'root',
    passwd = '',
    database = 'test_db',
)

mycursor = mydb.cursor()

sql = "INSERT INTO test (name,url) VALUES (%s,%s)"
val = ("ECUST","Xu Huan")
mycursor.execute(sql,val)

mydb.commit()

print(mycursor.rowcount,'记录插入成功')

1 记录插入成功

#插入多条记录
import mysql.connector

mydb = mysql.connector.connect(
    host = 'localhost',
    user = 'root',
    passwd = '',
    database = 'test_db',
)

mycursor = mydb.cursor()

sql = "INSERT INTO test (name,url) VALUES (%s,%s)"
val = [("ECUST","Xu Huan"),
      ("MIT","Wang Yizhuo"),
      ("JHU","Nawukere"),
      ]
mycursor.executemany(sql,val)#使用executemany()插入多条记录

mydb.commit()

print(mycursor.rowcount,'记录插入成功')

3 记录插入成功

import mysql.connector

mydb = mysql.connector.connect(
    host = 'localhost',
    user = 'root',
    passwd = '',
    database = 'test_db',
)

mycursor = mydb.cursor()

sql = "INSERT INTO test (name,url) VALUES (%s,%s)"
val = [("PKU","Smith"),
      ]
mycursor.executemany(sql,val)

mydb.commit()

print('一条记录已插入',mycursor.lastrowid)

一条记录已插入 7

查询数据

#查询数据可以用SELECT语句

import mysql.connector

mydb = mysql.connector.connect(
    host = 'localhost',
    user = 'root',
    passwd = '',
    database = 'test_db',
)

mycursor = mydb.cursor()

mycursor.execute("SELECT * FROM test")

myresult = mycursor.fetchall() #fetchall()获取所有记录

for i in myresult:
    print(i)

('ECUST', 'Xu Huan', 1)
('ECUST', 'Xu Huan', 2)
('ECUST', 'Xu Huan', 3)
('MIT', 'Wang Yizhuo', 4)
('JHU', 'Nawukere', 5)
('PKU', 'Smith', 6)
('PKU', 'Smith', 7)

#也可以读取指定的字段数据

import mysql.connector

mydb = mysql.connector.connect(
    host = 'localhost',
    user = 'root',
    passwd = '',
    database = 'test_db',
)

mycursor = mydb.cursor()

mycursor.execute("SELECT name,id FROM test")

myresult = mycursor.fetchall()

for i in myresult:
    print(i)

('ECUST', 1)
('ECUST', 2)
('ECUST', 3)
('MIT', 4)
('JHU', 5)
('PKU', 6)
('PKU', 7)

#如果只想读取一条数据，可以使用fetchone()方法

import mysql.connector

mydb = mysql.connector.connect(
    host = 'localhost',
    user = 'root',
    passwd = '',
    database = 'test_db',
)

mycursor = mydb.cursor()

mycursor.execute("SELECT * FROM test")

myresult = mycursor.fetchone() 

print(myresult)

('ECUST', 'Xu Huan', 1)

#对读取的数据有条件限制，可以使用where语句

import mysql.connector

mydb = mysql.connector.connect(
    host = 'localhost',
    user = 'root',
    passwd = '',
    database = 'test_db',
)

mycursor = mydb.cursor()

mycursor.execute("SELECT * FROM test WHERE name = 'ECUST'")

myresult = mycursor.fetchall() 

for i in myresult:
    print(i)

('ECUST', 'Xu Huan', 1)
('ECUST', 'Xu Huan', 2)
('ECUST', 'Xu Huan', 3)

#也可以使用通配符%

import mysql.connector

mydb = mysql.connector.connect(
    host = 'localhost',
    user = 'root',
    passwd = '',
    database = 'test_db',
)

mycursor = mydb.cursor()

mycursor.execute("SELECT * FROM test WHERE name LIKE '%K%'")

myresult = mycursor.fetchall() 

for i in myresult:
    print(i)

('PKU', 'Smith', 6)
('PKU', 'Smith', 7)

#为了防止数据库查询发生SQL注入的攻击，可以使用%s占位符转义查询的条件

import mysql.connector

mydb = mysql.connector.connect(
    host = 'localhost',
    user = 'root',
    passwd = '',
    database = 'test_db',
)

mycursor = mydb.cursor()

sql = "SELECT * FROM test WHERE name = %s"
na = ('PKU',)

mycursor.execute(sql, na)

myresult = mycursor.fetchall() 

for i in myresult:
    print(i)

('PKU', 'Smith', 6)
('PKU', 'Smith', 7)

#排序

import mysql.connector

mydb = mysql.connector.connect(
    host = 'localhost',
    user = 'root',
    passwd = '',
    database = 'test_db',
)

mycursor = mydb.cursor()

mycursor.execute("SELECT * FROM test ORDER BY url")

myresult = mycursor.fetchall() 

for i in myresult:
    print(i)

('JHU', 'Nawukere', 5)
('PKU', 'Smith', 6)
('PKU', 'Smith', 7)
('MIT', 'Wang Yizhuo', 4)
('ECUST', 'Xu Huan', 1)
('ECUST', 'Xu Huan', 2)
('ECUST', 'Xu Huan', 3)

#对数据基于某属性降序排序

import mysql.connector

mydb = mysql.connector.connect(
    host = 'localhost',
    user = 'root',
    passwd = '',
    database = 'test_db',
)

mycursor = mydb.cursor()

mycursor.execute("SELECT * FROM test ORDER BY name DESC")

myresult = mycursor.fetchall() 

for i in myresult:
    print(i)

('PKU', 'Smith', 6)
('PKU', 'Smith', 7)
('MIT', 'Wang Yizhuo', 4)
('JHU', 'Nawukere', 5)
('ECUST', 'Xu Huan', 1)
('ECUST', 'Xu Huan', 2)
('ECUST', 'Xu Huan', 3)

#读取指定数量条数据
#限制读取数据起始数据
import mysql.connector

mydb = mysql.connector.connect(
    host = 'localhost',
    user = 'root',
    passwd = '',
    database = 'test_db',
)

mycursor = mydb.cursor()

mycursor.execute("SELECT * FROM test LIMIT 4 OFFSET 2")
#用LIMIT语句指定查询数据量
#用OFFSET语句限制起始位置

myresult = mycursor.fetchall() 

for i in myresult:
    print(i)

('ECUST', 'Xu Huan', 3)
('MIT', 'Wang Yizhuo', 4)
('JHU', 'Nawukere', 5)
('PKU', 'Smith', 6)

删除记录

#使用DELETE FROM语句删除记录
import mysql.connector

mydb = mysql.connector.connect(
    host = 'localhost',
    user = 'root',
    passwd = '',
    database = 'test_db',
)

mycursor = mydb.cursor()

mycursor.execute("DELETE FROM test WHERE name LIKE '%K%'")

mydb.commit()
 
print(mycursor.rowcount, " 条记录删除")

2  条记录删除

#为了防止数据库查询发生 SQL 注入的攻击，我们可以使用 %s 占位符来转义删除语句的条件

import mysql.connector

mydb = mysql.connector.connect(
    host = 'localhost',
    user = 'root',
    passwd = '',
    database = 'test_db',
)

mycursor = mydb.cursor()

sql = "DELETE FROM test WHERE name = %s"
na = ("ECUST",)

mycursor.execute(sql,na)

mydb.commit()
 
print(mycursor.rowcount, " 条记录删除")

3  条记录删除

更新表数据

import mysql.connector

mydb = mysql.connector.connect(
    host = 'localhost',
    user = 'root',
    passwd = '',
    database = 'test_db',
)

mycursor = mydb.cursor()


sql = "UPDATE test SET name = 'princeton' WHERE name = 'JHU'"
 
mycursor.execute(sql)

mydb.commit()

print(mycursor.rowcount,'条记录被修改')

2 条记录被修改

#为了防止数据库查询发生 SQL 注入的攻击，我们可以使用 %s 占位符来转义更新语句的条件
import mysql.connector

mydb = mysql.connector.connect(
    host = 'localhost',
    user = 'root',
    passwd = '',
    database = 'test_db',
)

mycursor = mydb.cursor()


sql = "UPDATE test SET name = %s WHERE name = %s"
na = ('JHU','princeton')
 
mycursor.execute(sql,na)

mydb.commit()

print(mycursor.rowcount,'条记录被修改')

2 条记录被修改

删除表

#使用DROP TABLE语句删除表，使用IF EXISTS关键字判断表是否尊在
import mysql.connector

mydb = mysql.connector.connect(
    host = 'localhost',
    user = 'root',
    passwd = '',
    database = 'test_db',
)

mycursor = mydb.cursor()

sql = 'DROP TABLE IF EXISTS test'

mycursor.execute(sql)