通过SQL Alchemy中的直通表插入多对多关联

from sqlalchemy import Column, Integer, String
from sqlalchemy.ext.declarative import declarative_base

Base = declarative_base()

class User(Base):
    __tablename__ = 'users'
    
    id = Column(Integer, primary_key=True)
    name = Column(String)
    
class Role(Base):
    __tablename__ = 'roles'
    
    id = Column(Integer, primary_key=True)
    name = Column(String)

from sqlalchemy import Column, Integer, ForeignKey
from sqlalchemy.orm import relationship

class UserRole(Base):
    __tablename__ = 'user_roles'
    
    user_id = Column(Integer, ForeignKey('users.id'), primary_key=True)
    role_id = Column(Integer, ForeignKey('roles.id'), primary_key=True)
    
    user = relationship("User", backref="user_roles")
    role = relationship("Role", backref="user_roles")

from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker

engine = create_engine('数据库连接字符串')
Session = sessionmaker(bind=engine)
session = Session()

# 创建用户和角色实例
user1 = User(name='User1')
user2 = User(name='User2')
role1 = Role(name='Role1')
role2 = Role(name='Role2')

# 建立多对多关联
user_role1 = UserRole(user=user1, role=role1)
user_role2 = UserRole(user=user1, role=role2)
user_role3 = UserRole(user=user2, role=role1)

# 将关联关系添加到会话中
session.add(user_role1)
session.add(user_role2)
session.add(user_role3)

# 提交会话，将关联关系插入数据库
session.commit()