OperationalError: (OperationalError) no such column

问题

I have a problem. I have to do this query:

@app.route('/api/subscriptions/<string:id>', methods=('DELETE',))
@decorators.login_required
def delete_subscription(id):
    dbsession = DBSession()
    session = Session()
    favorit = (dbsession.query(StudentsFavorites)
      .filter(Exams.number == str(id))
      .filter(StudentsFavorites.exam_id)
      .filter(Students.id == StudentsFavorites.student_id)
      .filter(Students.id == str(session.get_user_id()))
      .delete()         )
    dbsession.flush()
    return jsonify(error=False)

But when I do this query I get this exception:

OperationalError: (OperationalError) no such column: exams.number u'DELETE FROM students_favorites WHERE exams.number = ? AND students_favorites.exam_id AND students.id = students_favorites.student_id AND students.id = ?' ('123123123', 'a24213')

The tables are very big and got lots of information, so i can't post all of it. But this query works:

@app.route('/api/subscriptions/<string:id>', methods=('PUT',))
@decorators.login_required
def add_subscription(id):
    dbsession = DBSession()
    session = Session()
    examID = (dbsession.query(Exams.id)
     .filter(Exams.number == id).first()
     )
    favorit=StudentsFavorites(student_id=session.get_user_id(), exam_id=examID.id)
    dbsession.add(favorit)
    dbsession.flush()
    return jsonify(error=False)

Short view to the table:

table: Exams
rows: id, number (number is the id i put into the function)

table: StudentsFavorites
rows: student_id, exams_id

table: Students
rows: id

I really didn't understand, why he didn't find the number row in the exception.

EDIT:

Database StudentsFavorites:

class StudentsFavorites(Base):
    """N:M resolve model for the exams to the semester.
    """

    __tablename__ = "students_favorites"

    student_id = Column(Unicode(255), ForeignKey("students.id"), primary_key=True, autoincrement=False)

    exam_id = Column(Integer, ForeignKey("exams.id"),            primary_key=True, autoincrement=False)

    created_at = Column(DateTime, nullable = False, default = datetime.now)

    student = relationship("Students", uselist = False, lazy="joined")

    exam = relationship("Exams", uselist=False, lazy="joined")

Something like this? I tried this:

    (dbsession.query(StudentsFavorites)
           .filter(StudentsFavorites.exam.id == str(id))
           .filter(StudentsFavorites.student.id == str(session.get_user_id()))
           .delete()
 )

But got the error, that id didn't exist in exams / student

回答1:

You have two cases of the same problem. Your query has information for StudentFavorites which means it knows about StudentFavorites.student_id and StudentFaovrites.exams_id. It doesn't know anything about Students.id, Exames.id and Exames.number. In order for you to query a StudentFavorites object and have it know about those other values you're going to have to perform a sql join.

Join's can be a bit of a pain in the ass to get working in sqlalchemy (well... in regular sql as well). Since I don't know what your table schema is I can't talk about that but the view should look something like this.

@app.route('/api/subscriptions/<string:id>', methods=('DELETE',))
@decorators.login_required
def delete_subscription(id):
    dbsession = DBSession()
    session = Session()
    favorit = (dbsession.query(StudentsFavorites)
      .join(Exames)
      .join(students)
      .filter(Exams.number == str(id))
      .filter(StudentsFavorites.exam_id)
      .filter(Students.id == StudentsFavorites.student_id)
      .filter(Students.id == str(session.get_user_id()))
      .delete()         )
    dbsession.flush()
    return jsonify(error=False)

Alternatively, you can look into setting up Foreign key relationships in your table statements if you use the ORM to create your tables

The reason your second example works is because you're specifying a query over an exam table and only using values found in that table.

Response to Edit: Right now your table relationships aren't set up correctly. Specifically the sections: Many To Many and Deleting Rows from the Many to Many Table

This example code is explained in much more (and better) detail in the posted link but the basic idea is that you have a associate_table (in your case StudentFavorites) contains foreign keys which have a relationship which is specified in one or more of your other tables. I personally advise that you go with the table example and not the object example.

association_table = Table('association', Base.metadata,
    Column('left_id', Integer, ForeignKey('left.id')),
    Column('right_id', Integer, ForeignKey('right.id'))
)

class Parent(Base):
    __tablename__ = 'left'
    id = Column(Integer, primary_key=True)
    children = relationship("Child",
                    secondary=association_table,
                    backref="parents")

class Child(Base):
    __tablename__ = 'right'
    id = Column(Integer, primary_key=True)

来源：https://stackoverflow.com/questions/18329539/operationalerror-operationalerror-no-such-column