使用 SQLAlchemy 进行 ORM 映射

from sqlalchemy import create_engine, Column, Integer, String
from sqlalchemy.orm import sessionmaker
from sqlalchemy.ext.declarative import declarative_base

# 创建 engine
engine = create_engine('postgresql://username:password@localhost:5432/mydatabase')

# 创建 session
Session = sessionmaker(bind=engine)
session = Session()

# 创建 Base 对象
Base = declarative_base()

# 创建一个 User 类，用于映射 users 数据表
class User(Base):
    __tablename__ = 'users'
    id = Column(Integer, primary_key=True)
    name = Column(String)
    email = Column(String)

# 创建表
Base.metadata.create_all(engine)

# 添加数据
user = User(name='pidancode', email='pidancode@example.com')
session.add(user)
session.commit()

# 查询数据
users = session.query(User).all()
for user in users:
    print(user.id, user.name, user.email)

# 修改数据
user = session.query(User).filter(User.name=='pidancode').first()
user.email = 'pidancode@gmail.com'
session.commit()

# 删除数据
user = session.query(User).filter(User.name=='pidancode').first()
session.delete(user)
session.commit()

# 关闭 session
session.close()