A weak entity with many to many relationship with its owner SQL I have this patient table which is an owner entity:

CREATE TABLE PATIENT 
(
    FILE_NO NUMBER(4) PRIMARY KEY, 
    NAME VARCHAR2(25), 
    SEX VARCHAR2 (7), 
    BLOOD_GROUP VARCHAR2(3),
    ALLERGIES VARCHAR (30), 
    BIRTH_DATE DATE, 
    INSURANCE_COMPANY VARCHAR (30)
);


and the appointment table is the weak entity

CREATE TABLE APPOINTMENT 
(
    APP_NO NUMBER(4),
    FILE_NO NUMBER (4),
    FOREIGN KEY (FILE_NO) REFERENCES PATIENT(FILE_NO),
    CONSTRAINT APPOINTMENT_PK PRIMARY KEY (APP_NO,FILE_NO),
    DATE_TIME TIMESTAMP, 
    DOCTOR_NAME VARCHAR2(25), 
    DEPARTMENT_NAME VARCHAR2(25)
);


they have a many to many relationship. Is this a correct table for the relationship?

CREATE TABLE APPOINTED_TO 
(
    APP_NO NUMBER(4),
    FILE_NO NUMBER (4),
    CONSTRAINT APPOINTED_TO_PK PRIMARY KEY (APP_NO,FILE_NO),
    CONSTRAINT APP_TO_FK FOREIGN KEY (APP_NO,FILE_NO)
        REFERENCES APPOINTMENT(APP_NO,FILE_NO)
);


My teacher insists I make a third table for the relationship. I can't take out the FILE_NO from the Appointment table because it's a weak entity.

It didn't make sense to me that's why I wanted to ask for an outside opinion.
The FOREIGN KEY is not correct. You must create 2 of them. One the PATIENT table for the FILE_NO field and one on the APPOINTMENT table for the APP_NO field.

PAT_TO_FK FOREIGN KEY APT_PATIENT_FK (FILE_NO) REFERENCES PATIENT(FILE_NO)
APP_TO_FK FOREIGN KEY APT_APPOINTMENT_FK (APP_NO) REFERENCES APPOINTMENT(APP_NO)