migrating to mysql in django

I want to migrate from sqlite3 to MySQL in Django. First I used below command:

python manage.py dumpdata > datadump.json

then I changed the settings of my Django application and configured it with my new MySQL database. Finally, I used the following command:

python manage.py loaddata datadump.json

but I got this error :

integrityError: Problem installing fixtures: The row in table'django_admin_log' with primary key '20' has an invalid foregin key: django_admin_log.user_id contains a value '19' that does not have a corresponding value in auth_user.id.