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  • sqlalchemy多对多查询

    # coding:utf-8
    from sqlalchemy import create_engine, Column, String, Integer, ForeignKey, Table
    from sqlalchemy.ext.declarative import declarative_base
    from sqlalchemy.orm import sessionmaker, relationship
    
    DB_URI = "mysql+pymysql://root:123123sdt@127.0.0.1:3306/xiachufang"
    engine = create_engine(DB_URI)
    Base = declarative_base(engine)
    session = sessionmaker(engine)()
    
    # 创建一个多对多的关系(老师与学生的关系)需要创建一个中间表
    # 创建一个中间表
    teacher_classes = Table(
        "teacher_classes",
        Base.metadata,
        Column("teacher_id", Integer, ForeignKey("teacher.id"), nullable=False, primary_key=True),
        Column("classes_id", Integer, ForeignKey("classes.id"), nullable=False, primary_key=True)
    )
    
    
    # 创建老师的映射
    class Teacher(Base):
        __tablename__ = "teacher"
        id = Column(Integer, primary_key=True, autoincrement=True)
        teacher_name = Column(String(100))
        classes = relationship("Classes", secondary=teacher_classes)
    
        def __repr__(self):
            return "<Teacher id='%s' teacher_name='%s'>" % (self.id, self.teacher_name)
    
    
    # 创建学生的映射
    class Classes(Base):
        __tablename__ = "classes"
        id = Column(Integer, primary_key=True, autoincrement=True)
        classes_name = Column(String(100))
        teacher = relationship("Teacher", secondary=teacher_classes)
    
        def __repr__(self):
            return "<Classes id='%s' classes_name='%s'>" % (self.id, self.classes_name)
    
    #
    # # 创建数据库
    # Base.metadata.create_all()
    
    # # 创建两个老师
    # teacher1 = Teacher(teacher_name='admin')
    # teacher2 = Teacher(teacher_name='grunt')
    # teacher3 = Teacher(teacher_name='shuihen')
    
    # # 创建两门课程
    # classes1 = Classes(classes_name="java")
    # classes2 = Classes(classes_name="python")
    #
    # # 添加数据
    # teacher1.classes = [classes1,classes2]
    # teacher2.classes = [classes1,classes2]
    # teacher3.classes = [classes1]
    # session.add(teacher1)
    # session.add(teacher2)
    # session.add(teacher3)
    # session.commit()
    
    # # 查询下数据(根据老师查询课程)
    # # teacher = session.query(Teacher).first()
    # # print teacher.classes
    #
    # # 根据课程查询老师
    # classes = session.query(Classes).get(1)
    # print classes.teacher
    #
    # # 根据老师查询课程
    # teacher = session.query(Teacher).get(3)
    # print teacher.classes
    

      

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  • 原文地址:https://www.cnblogs.com/pythonClub/p/9852831.html
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