Création de tables en MySQL en Python 3.4

Question

Je cours un serveur via Apache en utilisant Python 3.4 comme un cgi et un serveur de base de données MySQL sur Windows 10. Lorsque j'essaye d'exécuter ma fonction pour créer la base de données, j'obtiens l'erreur:

DatabaseError: 1005 (HY000): Can't create table `testdb`.`studentexam` (errno: 150 
"Foreign key constraint is incorrectly formed") 

la fonction de création de la base de données

import mysql.connector as conn 

#connect to server 
db=conn.connect(host="localhost",user="root",password="") 
cursor=db.cursor() 
#create database 
cursor.execute("""CREATE DATABASE IF NOT EXISTS Testdb""") 
db.commit() 
#use database 
cursor.execute("""USE Testdb""") 
db.commit() 
#create Teacher table 
cursor.execute("""CREATE TABLE IF NOT EXISTS Teacher(
    TeacherUsername VARCHAR(255) PRIMARY KEY, 
    TeacherPassword TEXT)""") 
db.commit() 
#create student table 
cursor.execute("""CREATE TABLE IF NOT EXISTS Student(
    StudentNo INT PRIMARY KEY, 
    StudentSurname TEXT, 
    StudentForename TEXT, 
    StudentTeacher VARCHAR(255), 
    StudentPassword TEXT, 
    FOREIGN KEY(StudentTeacher) REFERENCES Teacher(TeacherUsername))""") 
db.commit() 
#create exam table 
cursor.execute("""CREATE TABLE IF NOT EXISTS Exam(
    TestName VARCHAR(255) PRIMARY KEY, 
    TestTotalMarks TEXT, 
    Teacher VARCHAR(255), 
    FOREIGN KEY(Teacher) REFERENCES Teacher(TeacherUsername))""") 
db.commit() 
#create StudentExam table 
cursor.execute("""CREATE TABLE IF NOT EXISTS StudentExam(
    TestName VARCHAR(255), 
    StudentID INT, 
    StudentTotalMarks INT, 
    PRIMARY KEY(TestName,StudentID), 
    FOREIGN KEY(TestName) REFERENCES Exam(TestName), 
    FOREIGN KEY(StudentID) REFERENCES Student(StudentID))""") 
db.commit() 
#create ExamSection table 
cursor.execute("""CREATE TABLE IF NOT EXISTS ExamSection(
    TestName VARCHAR(255), 
    SectionID INT, 
    PRIMARY KEY(TestName,SectionID), 
    FOREIGN KEY(TestName) REFERENCES Exam(TestName), 
    FOREIGN KEY(SectionID) REFERENCES Section(SectionID))""") 
db.commit() 
#create Section table 
cursor.execute("""CREATE TABLE IF NOT EXISTS Section(
    SectionID INT PRIMARY KEY, 
    SectionName TEXT, 
    SectionTotalMarks INT)""") 
db.commit() 
#create Question table 
cursor.execute("""CREATE TABLE IF NOT EXISTS Question(
    QuestionID INT PRIMARY KEY, 
    SectionID VARCHAR(255), 
    Image TEXT, 
    Question TEXT, 
    PossibleAnswer TEXT, 
    CorrectAnswer TEXT, 
    QuestionType TEXT, 
    FOREIGN KEY(SectionID) REFERENCES Section(SectionID))""") 
db.commit() 
#create QuestionResults Table 
cursor.execute("""CREATE TABLE IF NOT EXISTS QuestionResults(
    QuestionID INT, 
    StudentID INT, 
    SectionID VARCHAR(255), 
    StudentAnswer TEXT, 
    PRIMARY KEY(QuestionID,StudentID), 
    FOREIGN KEY(QuestionID) REFERENCES Question(QuestionID) 
    FOREIGN KEY(StudentID) REFERENCES Student(StudentID))""") 
db.commit() 
#create Revision table 
cursor.execute("""CREATE TABLE IF NOT EXISTS Revision(
    RevisionID INT PRIMARY KEY, 
    RevisionSheet TEXT, 
    TeacherUsername VARCHAR(255), 
    FOREIGN KEY(TeacherUsername) REFERENCES Teacher(TeacherUsername))""") 
db.commit() 
#create StudentRevition table 
cursor.execute("""CREATE TABLE IF NOT EXISTS StudentRevision(
    RevisionID INT, 
    StudentID INT, 
    PRIMARY KEY(RevisionID,StudentID), 
    FOREIGN KEY(RevisionID) REFERENCES Revision(RevisionID), 
    FOREIGN KEY(StudentID) REFERENCES Student(StudentID))""") 
db.commit() 
#create StudentResults table 
cursor.execute("""CREATE TABLE IF NOT EXISTS StudentResults(
    SectionID VARCHAR(255), 
    StudentID INT, 
    StudentSectionMarks INT, 
    PRIMARY KEY(SectionID,StudentID), 
    FOREIGN KEY(SectionID) REFERENCES Section(SectionID), 
    FOREIGN KEY(StudentID) REFERENCES Student(StudentID))""") 
db.commit() 
cursor.close()   

EDIT: Je Changed StudentNo à StudentID et maintenant obtenir l'erreur:

DatabaseError: 1005 (HY000): Can't create table `testdb`.`examsection` (errno: 150 
"Foreign key constraint is incorrectly formed") 

Answer 1

Lors de la création de StudentExam, vous faites référence à Student.StudentId qui n'existe pas. Il semble que vous préfériez référencer Student.StudentNo.

modifier:

Lorsque vous créez ExamSection, vous faites référence à la table de la section, qui n'existe pas encore. Déplacez l'état de création de section vers le haut afin qu'il s'exécute et valide avant de créer ExamSection.

Answer 2

Modifier ceci:

#create student table 
cursor.execute("""CREATE TABLE IF NOT EXISTS Student(
StudentNo INT PRIMARY KEY, 
StudentSurname TEXT, 
StudentForename TEXT, 
StudentTeacher VARCHAR(255), 
StudentPassword TEXT, 
FOREIGN KEY(StudentTeacher) REFERENCES Teacher(TeacherUsername))""") 
db.commit() 

à ceci:

#create student table 
cursor.execute("""CREATE TABLE IF NOT EXISTS Student(
StudentID INT PRIMARY KEY, 
StudentSurname TEXT, 
StudentForename TEXT, 
StudentTeacher VARCHAR(255), 
StudentPassword TEXT, 
FOREIGN KEY(StudentTeacher) REFERENCES Teacher(TeacherUsername))""") 
db.commit()