一对多关系sqlalchemy id

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

# 创建数据库引擎
engine = create_engine('mysql+pymysql://username:password@host:port/database')

# 创建会话工厂
Session = sessionmaker(bind=engine)

# 创建基类
Base = declarative_base()

# 定义一对多关系的模型
class Department(Base):
    __tablename__ = 'departments'
    id = Column(Integer, primary_key=True)
    name = Column(String(50))
    employees = relationship('Employee', backref='department')

class Employee(Base):
    __tablename__ = 'employees'
    id = Column(Integer, primary_key=True)
    name = Column(String(50))
    department_id = Column(Integer, ForeignKey('departments.id'))

# 创建表
Base.metadata.create_all(engine)

# 创建会话
session = Session()

# 创建部门和员工
department = Department(name='IT')
employee1 = Employee(name='John')
employee2 = Employee(name='Jane')

# 建立关联
department.employees.append(employee1)
department.employees.append(employee2)

# 提交事务
session.add(department)
session.commit()

# 查询部门及其员工
department = session.query(Department).filter_by(name='IT').first()
print(department.name)
for employee in department.employees:
    print(employee.name)

# 关闭会话
session.close()