在Python中查询多个数据库表数据，不同的数据库有不同的操作方式，以下以常见的MySQL和SQLite为例进行说明。 #### MySQL 使用`pymysql`库，以下是查询多个表数据的示例代码： ```python import pymysql # 连接数据库 conn = pymysql.connect(host='localhost', user='root', password='password', database='your_database') cursor = conn.cursor() # 多表查询语句 query = "SELECT * FROM table1 JOIN table2 ON table1.id = table2.table1_id" # 执行查询 cursor.execute(query) # 获取查询结果 results = cursor.fetchall() # 输出结果 for row in results: print(row) # 关闭连接 cursor.close() conn.close() ``` #### SQLite 使用`sqlite3`库，示例代码如下： ```python import sqlite3 # 连接数据库 conn = sqlite3.connect('your_database.db') cursor = conn.cursor() # 多表查询语句 query = "SELECT * FROM table1 JOIN table2 ON table1.id = table2.table1_id" # 执行查询 cursor.execute(query) # 获取查询结果 results = cursor.fetchall() # 输出结果 for row in results: print(row) # 关闭连接 cursor.close() conn.close() ``` 如果使用`SQLAlchemy`这种ORM（对象关系映射）库，以多表关联查询为例，示例代码如下： ```python from sqlalchemy import create_engine, Column, Integer, String, ForeignKey from sqlalchemy.orm import sessionmaker, relationship from sqlalchemy.ext.declarative import declarative_base # 创建基类 Base = declarative_base() # 定义表模型 class Role(Base): __tablename__ = 'roles' id = Column(Integer, primary_key=True) name = Column(String) users = relationship("User", back_populates="role") class User(Base): __tablename__ = 'users' id = Column(Integer, primary_key=True) name = Column(String) role_id = Column(Integer, ForeignKey('roles.id')) role = relationship("Role", back_populates="users") # 创建数据库引擎 engine = create_engine('sqlite:///test.db') # 创建表 Base.metadata.create_all(engine) # 创建会话 Session = sessionmaker(bind=engine) session = Session() # 关联查询示例 role1 = session.query(Role).get(1) user_list = role1.users for user in user_list: print(user.name) # 关闭会话 session.close() ```