flask 多对多关系主从表之间查询

叁歲伎倆 2022-05-08 09:44 238阅读 0赞

model层

class Studentnew(db.Model):
        id = db.Column(db.Integer,primary_key=True)
        name = db.Column(db.String(20),unique=True)
    
        #添加多对多的反向引用,必须使用secondary指定中间关联表
        courses = db.relationship('Course', secondary='xuankebiao',
                                  backref=db.backref('students', lazy='dynamic'), lazy='dynamic')

class Course(db.Model):
        id = db.Column(db.Integer,primary_key=True)
        name = db.Column(db.String(20),unique=True)
    
    # 学生选课表(中间关联表)，不需要用户维护
    xuankebiao = db.Table('xuankebiao',
        db.Column('student_id', db.Integer, db.ForeignKey('studentnew.id')),
        db.Column('course_id', db.Integer, db.ForeignKey('course.id')),
    )

views函数:

#多对多关系查询
    @blue.route('/manytomany/<id>/')
    def manytumany(id):
        #根据学生找课程
        # student =Studentnew.query.get(id)
        # courses = student.courses.all()
        # return ','.join(c.name for c in courses)
    
        #根据课程找学生
        course = Course.query.get(id)
        stus = course.students.all()
        return ','.join((i.name for i in stus))
    
    #多对多添加删除
    @blue.route('/many_many/')
    def many_many():
        student = Studentnew.query.get(1)
        course = Course.query.get(5)
        #学生选课
        # student.courses.append(course)
        # return student.name + '选了' + course.name
    
        #取消选课
        student.courses.remove(course)
        return student.name + '取消' + course.name