三十六：数据库之SQLAlchemy外建之一对一关系

relationship()的uselist参数默认为True，即一对多，如果要一对一，则需让uselist=False

准备工作

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

# 数据库信息
host = '127.0.0.1'
port = '3306'
database = 'db_to_sqlalchemy'
username = 'root'
password = '123456'

# 数据库类型+连接数据库的插件，这里使用的pymysql
DB_URI = f'mysql+pymysql://{username}:{password}@{host}:{port}/{database}'

engine = create_engine(DB_URI)  # 创建引擎
Base = declarative_base(engine)  # 使用declarative_base创建基类
session = sessionmaker(engine)()

模型关系

class User(Base):
    __tablename__ = 'user'
    id = Column(Integer, primary_key=True, autoincrement=True)
    username = Column(String(50), nullable=Float)

    u_info = relationship('UserInfo', uselist=False)  # 关闭一对多关系，即一对一

    def __repr__(self):
        return f'User(username: {self.username})'


class UserInfo(Base):
    __tablename__ = 'user_info'
    id = Column(Integer, primary_key=True, autoincrement=True)
    school = Column(String(50))
    uid = Column(Integer, ForeignKey('user.id'))

    user = relationship('User')

Base.metadata.drop_all()  # 删除所有表
Base.metadata.create_all()  # 创建表

user = User(username='abc')
info1 = UserInfo(school='xxxxx')
user.u_info = info1

session.add(user)
session.commit()

若采用一对多的关系则会报错

优化