【Python 操作 MySQL 数据库】

在 Python 中操作 MySQL 数据库主要通过 pymysql 或 mysql-connector-python 库实现。以下是完整的技术指南，包含连接管理、CRUD 操作和最佳实践：

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一、环境准备

1. 安装驱动库

pip install pymysql          # 推荐（纯Python实现）
# 或
pip install mysql-connector-python  # Oracle官方驱动

2. 数据库准备

CREATE DATABASE testdb;
USE testdb;CREATE TABLE users (id INT AUTO_INCREMENT PRIMARY KEY,username VARCHAR(50) UNIQUE NOT NULL,email VARCHAR(100) NOT NULL,created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);

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二、连接管理

1. 基础连接

import pymysql# 建立连接
conn = pymysql.connect(host='localhost',user='root',password='your_password',database='testdb',charset='utf8mb4',cursorclass=pymysql.cursors.DictCursor  # 返回字典格式结果
)

2. 上下文管理器（推荐）

with pymysql.connect(host='localhost', user='root', password='your_pwd', database='testdb') as conn:with conn.cursor() as cursor:# 执行SQL操作pass# 连接在此处自动提交/回滚（取决于autocommit设置）

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三、CRUD 操作

1. 查询数据

def get_user(username):try:with conn.cursor() as cursor:sql = "SELECT * FROM users WHERE username = %s"cursor.execute(sql, (username,))result = cursor.fetchone()  # 获取单条记录return resultexcept pymysql.MySQLError as e:print(f"数据库错误: {e}")return Noneuser = get_user("john_doe")
print(user)  # 输出: {'id': 1, 'username': 'john_doe', ...}

2. 插入数据

def create_user(username, email):try:with conn.cursor() as cursor:sql = """INSERT INTO users (username, email) VALUES (%s, %s)"""cursor.execute(sql, (username, email))conn.commit()  # 显式提交事务return cursor.lastrowid  # 返回自增IDexcept pymysql.IntegrityError:print("用户名已存在")conn.rollback()return Nonenew_id = create_user("jane_smith", "[e-mail]")

3. 更新数据

def update_email(user_id, new_email):try:with conn.cursor() as cursor:sql = "UPDATE users SET email = %s WHERE id = %s"affected_rows = cursor.execute(sql, (new_email, user_id))conn.commit()return affected_rows > 0except pymysql.MySQLError:conn.rollback()return False

4. 批量操作

def batch_insert(users):try:with conn.cursor() as cursor:sql = "INSERT INTO users (username, email) VALUES (%s, %s)"cursor.executemany(sql, users)  # 批量执行conn.commit()return cursor.rowcountexcept pymysql.MySQLError:conn.rollback()return 0batch_insert([("user1", "[e-mail]"),("user2", "[e-mail]")
])

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四、高级技巧

1. 连接池管理

from dbutils.pooled_db import PooledDBpool = PooledDB(creator=pymysql,maxconnections=10,host='localhost',user='root',password='your_pwd',database='testdb'
)# 使用连接池获取连接
conn = pool.connection()

2. 存储过程调用

with conn.cursor() as cursor:cursor.callproc('get_user_stats', (1,))  # 调用存储过程result = cursor.fetchall()

3. 事务控制

try:with conn.cursor() as cursor:# 执行多个操作cursor.execute("UPDATE account SET balance = balance - 100 WHERE id = 1")cursor.execute("UPDATE account SET balance = balance + 100 WHERE id = 2")conn.commit()  # 显式提交事务
except:conn.rollback()  # 回滚所有操作

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五、安全实践

1. 防止SQL注入

• 永远使用参数化查询（不要拼接字符串）

  # 正确方式
  cursor.execute("SELECT * FROM users WHERE id = %s", (user_id,))# 危险方式（禁用！）
  cursor.execute(f"SELECT * FROM users WHERE id = {user_id}")
  

2. 敏感信息处理

• 使用环境变量存储密码：

  import os
  password = os.getenv('DB_PASSWORD')
  

3. 连接超时设置

conn = pymysql.connect(connect_timeout=5,  # 连接超时5秒read_timeout=10     # 读取超时10秒
)

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六、性能优化

1. 查询优化

• 添加索引：

  ALTER TABLE users ADD INDEX idx_email (email);
  

• 使用EXPLAIN分析查询：

  with conn.cursor() as cursor:cursor.execute("EXPLAIN SELECT * FROM users WHERE username = %s", ("john",))print(cursor.fetchall())
  

2. 结果集处理

• 分页查询：

  sql = "SELECT * FROM users LIMIT %s OFFSET %s"
  cursor.execute(sql, (page_size, (page-1)*page_size))
  

• 流式读取（大数据量）：

  with conn.cursor(pymysql.cursors.SSCursor) as cursor:  # 使用服务器端游标cursor.execute("SELECT * FROM large_table")for row in cursor:process(row)
  

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七、完整示例

import pymysql
from contextlib import contextmanager@contextmanager
def database_connection():conn = pymysql.connect(host='localhost',user='root',password='your_pwd',database='testdb',charset='utf8mb4')try:yield connfinally:conn.close()def main():with database_connection() as conn:with conn.cursor() as cursor:# 创建用户cursor.execute("""INSERT INTO users (username, email)VALUES (%s, %s)""", ("new_user", "[e-mail]"))user_id = cursor.lastrowid# 查询用户cursor.execute("SELECT * FROM users WHERE id = %s", (user_id,))print(cursor.fetchone())# 更新记录cursor.execute("""UPDATE users SET email = %s WHERE id = %s""", ("[e-mail]", user_id))conn.commit()if __name__ == "__main__":main()

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八、故障排查

1. 常见错误码

• 1045: 访问被拒绝（检查用户名/密码）
• 2003: 无法连接（检查主机/端口）
• 1062: 唯一键冲突
• 1146: 表不存在

2. 日志记录

import logging
logging.basicConfig(level=logging.DEBUG,format='%(asctime)s - %(levelname)s - %(message)s'
)# 在连接参数中添加
conn = pymysql.connect(..., cursorclass=pymysql.cursors.SSDictCursor,client_flag=pymysql.client.CLIENT.MULTI_STATEMENTS)

通过遵循这些实践，可以构建安全、高效的数据库交互应用。对于复杂场景，建议结合ORM框架（如SQLAlchemy）进行抽象层开发。