Question

我需要创建一个学生管理系统，该系统可以帮助多位老师教多位学生而多位学生可以有多位老师的方式进行联系。现在，我在.P.S。下创建了一个代码如果您认为有一种更好的方法来实现自己想要的目标，请进行指导，对于许多关系我是陌生的，并且互联网上有很多方法，这很令人困惑：

AssociationTable=db.Table('AssociationTable',
db.Column('id',db.Integer,primary_key=True),
db.Column('teacher_id',db.Integer,db.ForeignKey('Teacher.id')),
db.Column('student_id',db.Integer,db.ForeignKey('Student.id')))

class College(db.Model):
__tablename__='College'
id=db.Column(db.Integer,primary_key=True)
name=db.Column(db.String(30),unique=True,nullable=False)
departments=db.relationship('Department',backref='college',lazy=True)
students=db.relationship('Student',backref='student',lazy=True)
teachers=db.relationship('Teacher',backref='teacher',lazy=True)

def __repr__(self):
    return f"College(ID:{self.id}\nName:{self.name})"

class Department(db.Model):
__tablename__='Department'
id=db.Column(db.Integer,primary_key=True)
name=db.Column(db.String(30),nullable=False)
college=db.Column(db.Integer,db.ForeignKey('college.id'),nullable=False)
students=db.relationship('Student',backref='student',lazy=True)
teachers=db.relationship('Teacher',backref='teacher',lazy=True)

def __repr__(self):
    return f"Department(ID:{self.id}\nName:{self.name}\nCollege:{self.college})"

class Teacher(db.Model):
__tablename__='Teacher'
id=db.Column(db.Integer,primary_key=True)
name=db.Column(db.String(30),nullable=False)
username=db.Column(db.Integer,nullable=False,unique=True)
address=db.Column(db.String(80),nullable=False)
phone=db.Column(db.String(13),nullable=False)
students=db.relationship('Student',secondary=AssociationTable,backref='Teacher')
section=db.relationship('Student',backref='section',lazy=True)
department=db.Column(db.Integer,db.ForeignKey('department.id'),nullable=False)
college=db.Column(db.Integer,db.ForeignKey('college.id'),nullable=False)

def __repr__(self):
    return f"Teacher(ID:{self.id}\nName:{self.name}\nUsername:{self.username}\nAddress:{self.address}\nPhone:{self.phone},Section:{self.section}\nCollege:{self.college}\nDepartment:{self.department})"

class Student(db.Model):
__tablename__='Student'
id=db.Column(db.Integer,primary_key=True)
name=db.Column(db.String(30),nullable=False)
username=db.Column(db.Integer,nullable=False,unique=True)
address=db.Column(db.String(80),nullable=False)
phone=db.Column(db.String(13),nullable=False)
teachers=db.relationship('Teacher',secondary=AssociationTable,backref='Student')
section=db.Column(db.String(3),nullable=False)
department=db.Column(db.Integer,db.ForeignKey('department.id'),nullable=False)
college=db.Column(db.Integer,db.ForeignKey('college.id'),nullable=False)

def __repr__(self):
    return f"Student(ID:{self.id}\nName:{self.name}\nUsername:{self.username}\nAddress:{self.address}\nPhone:{self.phone},Section:{self.section}\nCollege:{self.college}\nDepartment:{self.department})"

错误是：

 db.create_all()
Traceback (most recent call last):
  File "", line 1, in 
  File "C:\Program Files (x86)\Python36-32\lib\site-packages\flask_sqlalchemy\__init__.py", line 963, in create_all
    self._execute_for_all_tables(app, bind, 'create_all')
  File "C:\Program Files (x86)\Python36-32\lib\site-packages\flask_sqlalchemy\__init__.py", line 955, in _execute_for_all_tables
    op(bind=self.get_engine(app, bind), **extra)
  File "C:\Program Files (x86)\Python36-32\lib\site-packages\sqlalchemy\sql\schema.py", line 4005, in create_all
    tables=tables)
  File "C:\Program Files (x86)\Python36-32\lib\site-packages\sqlalchemy\engine\base.py", line 1940, in _run_visitor
    conn._run_visitor(visitorcallable, element, **kwargs)
  File "C:\Program Files (x86)\Python36-32\lib\site-packages\sqlalchemy\engine\base.py", line 1549, in _run_visitor
    **kwargs).traverse_single(element)
  File "C:\Program Files (x86)\Python36-32\lib\site-packages\sqlalchemy\sql\visitors.py", line 121, in traverse_single
    return meth(obj, **kw)
  File "C:\Program Files (x86)\Python36-32\lib\site-packages\sqlalchemy\sql\ddl.py", line 736, in visit_metadata
    [t for t in tables if self._can_create_table(t)])
  File "C:\Program Files (x86)\Python36-32\lib\site-packages\sqlalchemy\sql\ddl.py", line 1095, in sort_tables_and_constraints
    dependent_on = fkc.referred_table
  File "C:\Program Files (x86)\Python36-32\lib\site-packages\sqlalchemy\sql\schema.py", line 3003, in referred_table
    return self.elements[0].column.table
  File "C:\Program Files (x86)\Python36-32\lib\site-packages\sqlalchemy\util\langhelpers.py", line 767, in __get__
    obj.__dict__[self.__name__] = result = self.fget(obj)
  File "C:\Program Files (x86)\Python36-32\lib\site-packages\sqlalchemy\sql\schema.py", line 1892, in column
    tablekey)
sqlalchemy.exc.NoReferencedTableError: Foreign key associated with column 'AssociationTable.student_id' could not find table 'Student' with which to generate a foreign key to target column 'id'

Answer 1

i将assocication_table定义放在文件末尾。

在Flask-SqlAlchemy中创建多对多关系

1 个答案: