python 操作MySQL数据库

文章目录

- 1. 安装 PyMySQL
- 2. 连接对象
- 3. 游标对象
- 4. 增删改操作
- - cursor.execute(sql)
  - cursor.executemany(sql, seq_of_params)
- 5. 查询操作
- 6. ORM编程
- - 常用 python ORM 库

learning from 《python web开发从入门到精通》

1. 安装 PyMySQL

conda 虚拟环境下安装 pip install pymysql

2. 连接对象

创建连接的一个 object

import pymysqltry:connection = pymysql.connect(host='localhost',user='root',password='123456',db='michaeldata',charset='utf8',cursorclass=pymysql.cursors.DictCursor  # 游标类型)print("连接成功：", connection)
except Exception as e:print("连接失败：", e)

输出：连接成功： <pymysql.connections.Connection object at 0x00000205AC8E96D0>

成功连接后，获取的连接对象，有很多方法，常用的如下：

cursor() 获取游标对象，操作数据库
commit() 提交事务
rollback() 回滚事务
close() 关闭数据库连接

3. 游标对象

cursor = connection.cursor()

游标对象的常用方法：

execute(operation, [, param]) 执行数据库操作，SQL语句
executemany(operation, 参数序列) 批量执行操作
fetchone() 获取查询结果集里的下一条
fetchmany(size) 获取指定数量的记录
fetchall() 获取所有记录
close() 关闭游标

操作流程实例：

import pymysqltry:connection = pymysql.connect(host='localhost',user='root',password='123456',db='michaeldata',charset='utf8',cursorclass=pymysql.cursors.DictCursor  # 游标类型)print("连接成功：", connection)
except Exception as e:print("连接失败：", e)# sql 语句
sql = '''
create table books(id int not null auto_increment,name varchar(255) not null,category varchar(50) not null,price decimal(10, 2) default '0',publish_time date default null,primary key (id)
) engine = InnoDB auto_increment=1 
default charset = utf8mb4 collate = utf8mb4_0900_ai_ci;
'''cursor = connection.cursor()  # 获取游标对象
cursor.execute(sql)  # 执行sql语句
cursor.close()  # 先关闭游标
connection.close()  # 再关闭连接，或者使用 with as

在这里插入图片描述

4. 增删改操作

对于增删改，使用 cursor.execute() 执行 SQL 语句后，默认不会自动提交，要使用 connection.commit() 提交
insert 语句使用 %s 作为占位符，可以防止 SQL注入

cursor.execute(sql)

import pymysqltry:connection = pymysql.connect(host='localhost',user='root',password='123456',db='michaeldata',charset='utf8',cursorclass=pymysql.cursors.DictCursor  # 游标类型)print("连接成功：", connection)
except Exception as e:print("连接失败：", e)# sql 语句
sql = '''
create table if not exists books(id int not null auto_increment,name varchar(255) not null,category varchar(50) not null,price decimal(10, 2) default '0',publish_time date default null,primary key (id)
) engine = InnoDB auto_increment=1 
default charset = utf8mb4 collate = utf8mb4_0900_ai_ci;
'''cursor = connection.cursor()  # 获取游标对象
cursor.execute(sql)  # 执行sql语句sql1 = 'insert into books(name, category, price, publish_time) values("python web开发", "python", "98.8", "2020-01-01")'
cursor.execute(sql1)  # 执行sql语句
connection.commit()  # connection 提交才能生效cursor.close()  # 先关闭游标
connection.close()  # 再关闭连接，或者使用 with as

在这里插入图片描述

cursor.executemany(sql, seq_of_params)

批量操作

import pymysqltry:connection = pymysql.connect(host='localhost',user='root',password='123456',db='michaeldata',charset='utf8',cursorclass=pymysql.cursors.DictCursor  # 游标类型)print("连接成功：", connection)
except Exception as e:print("连接失败：", e)# sql 语句
sql = '''
create table if not exists books(id int not null auto_increment,name varchar(255) not null,category varchar(50) not null,price decimal(10, 2) default '0',publish_time date default null,primary key (id)
) engine = InnoDB auto_increment=1 
default charset = utf8mb4 collate = utf8mb4_0900_ai_ci;
'''cursor = connection.cursor()  # 获取游标对象
cursor.execute(sql)  # 执行sql语句# sql1 = 'insert into books(name, category, price, publish_time) values("python web开发", "python", "98.8", "2020-01-01")'
# cursor.execute(sql1)  # 执行sql语句
# connection.commit()  # connection 提交才能生效# 数据列表
data = [("零基础学Python", 'Python', '79.80', '2018-5-20'),("Python从入门到精通", 'Python', '69.80', '2018-6-18'),("零基础学PHP", 'PHP', '69.80', '2017-5-21'),("PHP项目开发实战入门", 'PHP', '79.80', '2016-5-21'),("零基础学Java", 'Java', '69.80', '2017-5-21'),]
try:cursor.executemany('insert into books(name, category, price, publish_time) values(%s, %s, %s, %s)', data)connection.commit()  # connection 提交才能生效
except Exception as e:connection.rollback()  # 回滚cursor.close()  # 先关闭游标
connection.close()  # 再关闭连接，或者使用 with as

在这里插入图片描述

5. 查询操作

执行 select 查询，生成结果集，然后使用 fetchone/fetchmany/fetchall () 相关语句获取记录

import pymysqltry:connection = pymysql.connect(host='localhost',user='root',password='123456',db='michaeldata',charset='utf8',cursorclass=pymysql.cursors.DictCursor  # 游标类型)print("连接成功：", connection)
except Exception as e:print("连接失败：", e)# sql 语句
sql = "select * from books order by price"
with connection.cursor() as cursor:cursor.execute(sql)  # 执行sql语句result1 = cursor.fetchone()  # 获取查询结果result2 = cursor.fetchall()  # 获取查询结果print(result1)
print("*" * 10)
for res in result2:print(res)connection.close()  # 关闭连接

输出结果：

连接成功： <pymysql.connections.Connection object at 0x00000216C72696D0>
{'id': 5, 'name': 'Python从入门到精通', 'category': 'Python', 'price': Decimal('69.80'), 'publish_time': datetime.date(2018, 6, 18)}
**********
{'id': 6, 'name': '零基础学PHP', 'category': 'PHP', 'price': Decimal('69.80'), 'publish_time': datetime.date(2017, 5, 21)}
{'id': 8, 'name': '零基础学Java', 'category': 'Java', 'price': Decimal('69.80'), 'publish_time': datetime.date(2017, 5, 21)}
{'id': 4, 'name': '零基础学Python', 'category': 'Python', 'price': Decimal('79.80'), 'publish_time': datetime.date(2018, 5, 20)}
{'id': 7, 'name': 'PHP项目开发实战入门', 'category': 'PHP', 'price': Decimal('79.80'), 'publish_time': datetime.date(2016, 5, 21)}
{'id': 3, 'name': 'python web开发', 'category': 'python', 'price': Decimal('98.80'), 'publish_time': datetime.date(2020, 1, 1)}