title: IntegrityError Primary Key Invalid
body: <p>I am following sentdex's tutorials for django web development, however I have hit a wall - the error shows:</p>
  
  <blockquote>
    <p>django.db.utils.IntegrityError: The row in table 'main_tutorial' with primary key '1' has an invalid foreign key: main_tutorial.tutorial_series_id contains a value '1' that does not have a corresponding value in main_tutorialseries.id.</p>
  </blockquote>
  
  <p>I've tried removing <code>default=1</code>,  and <code>on_delete=models.SET_DEFAULT/CASCADE</code>.</p>
  
  <p>I've also tried deleting the SQL database, migrations.
  I've tried using SQ Browser for SQlite to try and change things.</p>
  
  <p>Sadly I've spent hours staring at this and trying to find an answer, any help would be greatly appreciated. Thanks!
  The code is :</p>
  
  <pre><code>from django.db import models
  from datetime import datetime
  
  
  class TutorialCategory(models.Model):
  
      tutorial_category = models.CharField(max_length=200)
      category_summary = models.CharField(max_length=200)
      category_slug = models.CharField(max_length=200, default=1)
  
      class Meta:
          # Gives the proper plural name for admin
          verbose_name_plural = "Categories"
  
      def __str__(self):
          return self.tutorial_category
  
  class TutorialSeries(models.Model):
      tutorial_series = models.CharField(max_length=200, default=1)
      tutorial_category = models.ForeignKey(TutorialCategory, default=1,
                                            verbose_name="Category", on_delete=models.SET_DEFAULT)
      series_summary = models.CharField(max_length=200)
  
      class Meta:
          # otherwise we get "Tutorial Seriess in admin"
          verbose_name_plural = "Series"
  
      def __str__(self):
          return self.tutorial_series
  
  
  class Tutorial(models.Model):
      tutorial_title = models.CharField(max_length=200)
      tutorial_content = models.TextField()
      tutorial_published = models.DateTimeField('date published')
  
      tutorial_series = models.ForeignKey(TutorialSeries, default=1, verbose_name="Series", on_delete=models.SET_DEFAULT)
      tutorial_slug = models.CharField(max_length=200)
      def __str__(self):
          return self.tutorial_title
  </code></pre>
  
  <p>Any details to help walk me through this obstacle would be greatly appreciated. Thanks!</p>