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How to access tables from a different schema in oracle 11g using django?

I have a user named mi_abc in oracle 11g.
The user do not have any table in the database but has access to all the tables in another schema sch_abc.
When I run a normal select query from sqldeveloper on the sch_abc schema from mi_abc, it works perfectly fine, but when I use django, I am always getting the error:-
django.db.utils.DatabaseError: ORA-00942: table or view does not exist
I tried to set the db_table = sch_abc.tableName and also set db_table = tableName but both gives me the same error. Any clue how to resolve this?
TRACE:-
Traceback (most recent call last):
File "C:\xxx\xxx\xxx\xxx\xxx\xxx\xxxx\lib\site-packages\django\core\handlers\exception.py", line 41, in inner
response = get_response(request)
File "C:\xxx\xxx\xxxx\xxxx\xxxx\Python\Python37\lib\site-packages\django\utils\deprecation.py", line 142, in __call__
response = self.process_response(request, response)
File "C:\xxxx\xxxx\xxx\xxx\xxx\Python\Python37\lib\site-packages\django\contrib\sessions\middleware.py", line 58, in process_response
request.session.save()
File "C:\xxx\xxxx\xxxx\xxxx\xxxxx\Python\Python37\lib\site-packages\django\contrib\sessions\backends\db.py", line 81, in save
return self.create()
File "C:\xxxx\xxxxx\xxxx\xxxx\xxxxx\Python\Python37\lib\site-packages\django\contrib\sessions\backends\db.py", line 50, in create
self._session_key = self._get_new_session_key()
File "C:\xxxx\xxxxx\xxxxx\xxxxx\xxxx\Python\Python37\lib\site-packages\django\contrib\sessions\backends\base.py", line 164, in _get_new_session_key
if not self.exists(session_key):
File "C:\xxx\xxx\xxx\xxx\xxx\Python\Python37\lib\site-packages\django\contrib\sessions\backends\db.py", line 46, in exists
return self.model.objects.filter(session_key=session_key).exists()
File "C:\xxx\xxx\xxx\xxx\xxx\Python\Python37\lib\site-packages\django\db\models\query.py", line 673, in exists
return self.query.has_results(using=self.db)
File "C:\xxx\xxx\xxx\xxx\xxx\Python\Python37\lib\site-packages\django\db\models\sql\query.py", line 517, in has_results
return compiler.has_results()
File "C:\xxx\xxx\xxx\xxx\xxx\Python\Python37\lib\site-packages\django\db\models\sql\compiler.py", line 858, in has_results
return bool(self.execute_sql(SINGLE))
File "C:\xxx\xxx\xxx\xxx\xxx\Python\Python37\lib\site-packages\django\db\models\sql\compiler.py", line 899, in execute_sql
raise original_exception
File "C:\xxx\xxx\xxx\xxx\xxx\Python\Python37\lib\site-packages\django\db\models\sql\compiler.py", line 889, in execute_sql
cursor.execute(sql, params)
File "C:\xxx\xxx\xxx\xxx\xxx\Python\Python37\lib\site-packages\django\db\backends\utils.py", line 79, in execute
return super(CursorDebugWrapper, self).execute(sql, params)
File "C:\xxx\xxx\xxx\xxx\xxx\Python\Python37\lib\site-packages\django\db\backends\utils.py", line 64, in execute
return self.cursor.execute(sql, params)
File "C:\xxx\xxx\xxx\xxx\xxx\Python\Python37\lib\site-packages\django\db\utils.py", line 94, in __exit__
six.reraise(dj_exc_type, dj_exc_value, traceback)
File "C:\xxx\xxx\xxx\xxx\xxx\Python\Python37\lib\site-packages\django\utils\six.py", line 685, in reraise
raise value.with_traceback(tb)
File "C:\xxx\xxx\xxx\xxx\xxx\Python\Python37\lib\site-packages\django\db\backends\utils.py", line 64, in execute
return self.cursor.execute(sql, params)
File "C:\xxx\xxx\xxx\xxx\xxx\Python\Python37\lib\site-packages\django\db\backends\oracle\base.py", line 497, in execute
return self.cursor.execute(query, self._param_generator(params))
django.db.utils.DatabaseError: ORA-00942: table or view does not exist

Well, I resolved the issue and let me tell you there is no straight way to do it in django. The problem with my application was, I was using the authetication features of django and also session handling. All these tables are created by django directly on the initial migration. So, there is no existence of them in the models.py file that you can simply append the schema name and ask your application to connect to the table of that schema.
What I ended up doing is, I created private synonyms to all the tables of the other schema which actually contained those tables. If you do this, you don't have to change anything in your django code. Your application will simply work because oracle will do the dirty work of actually connecting to the proper table. You will merely call the table in your application as if its your own. In this way when django looks for tables like django_session, auth_user etc, it simply queries it like it always does and oracle redirects it to the actual tables present in another schema.
Hope this helps people who face this issue in the future.

This is by no means officially supported, but this works in Postgres:
class Meta:
managed = False
db_table = 'schema\".\"table'
It took some trial and error for Postgres, but you can probably do something similar for Oracle. This is because the Postgres engine quotes object names, and this fakes the quoting mechanism out.
UPDATE:
After doing some digging, I found this for Oracle (modified for Python 3):
class Meta:
db_table = '"SCHEMA"."TABLE_NAME"'
Source: https://code.djangoproject.com/ticket/14136
I would recommend keeping managed = False unless you really know what you're doing. Good luck!

You can set the required schema, before executing the command. and then go back to public schema once the queryset is processed.
from django.db import connection
connection.set_schema(schema_name)

Django Foreign Key of Auth.User - column "user_id" does not exist

UPDATE:
This is probably a better representation of my question:
Using loadtestdata, how do you populate the auth.User database? I just want to populate the database with bogus users, and simulations that are linked to those bogus users.
I have looked at all relevant resources but I'm unable to make any headway.
Situation:
I am building a simulation model using Django and am looking to store simulation data as well as sets of parameter data. Many sets of simulation data should be linked to each user, and many sets of parameter data can be linked to each simulation. Thus, I have tried to model this under 'models.py' of my Django app.
from django.db import models
from django.conf import settings
# Create your models here.
class Simulation(models.Model):
user = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE, )
date = models.DateTimeField()
# Each simulation has only one graph
# Graphing parameters
hill_num = models.CharField(max_length=3)
div_type = models.CharField(max_length=10)
s3_url = models.CharField(max_length=256)
def __str__(self):
return str(self.sim_id)
class Parameter(models.Model):
# Each simulation can have many sets of simulation parameters
simulation = models.ForeignKey('Simulation', on_delete=models.CASCADE)
lsp = models.PositiveIntegerField()
plots = models.PositiveIntegerField()
pioneer = models.BooleanField()
neutral = models.BooleanField()
# for pioneers
p_max = models.PositiveIntegerField()
p_num = models.PositiveIntegerField()
p_start = models.PositiveIntegerField()
# for non-pioneers
np_max = models.PositiveIntegerField()
np_num = models.PositiveIntegerField()
np_start = models.PositiveIntegerField()
def __str__(self):
return str(self.param_id)
./manage.py makemigrations works but when I try to populate the database with python manage.py loadtestdata auth.User:10 divexplorer.Simulation:40 divexplorer.Parameter:300, it throws this error:
auth.User(pk=72): JshtkqSzw3
auth.User(pk=73): QwPfxJc_KS1k5sgH5BN98J
auth.User(pk=74): fuEhnZ
auth.User(pk=75): a
auth.User(pk=76): XjVXXLYGz3MJSfmZ54wGxXo
auth.User(pk=77): fhOWIp
auth.User(pk=78): 5tkEhKOjX2UUbFe
auth.User(pk=79): JgG4Y4PqkcapNJJOlFW1LOQ
auth.User(pk=80): fhRmfQHNim4zM8hGPzpYdkwaHI7
auth.User(pk=81): cEPQtyByKdUs8Gw58DrfNtpsCRB_
Traceback (most recent call last):
File "manage.py", line 22, in <module>
execute_from_command_line(sys.argv)
File "/Users/evanma/anaconda/lib/python2.7/site-packages/django/core/management/__init__.py", line 363, in execute_from_command_line
utility.execute()
File "/Users/evanma/anaconda/lib/python2.7/site-packages/django/core/management/__init__.py", line 355, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/Users/evanma/anaconda/lib/python2.7/site-packages/django/core/management/base.py", line 283, in run_from_argv
self.execute(*args, **cmd_options)
File "/Users/evanma/anaconda/lib/python2.7/site-packages/django/core/management/base.py", line 330, in execute
output = self.handle(*args, **options)
File "/Users/evanma/anaconda/lib/python2.7/site-packages/django/utils/decorators.py", line 185, in inner
return func(*args, **kwargs)
File "/Users/evanma/anaconda/lib/python2.7/site-packages/autofixture/management/commands/loadtestdata.py", line 225, in handle
autofixture.create(model, count, **kwargs)
File "/Users/evanma/anaconda/lib/python2.7/site-packages/autofixture/__init__.py", line 136, in create
return autofixture.create(count, **create_kwargs)
File "/Users/evanma/anaconda/lib/python2.7/site-packages/autofixture/base.py", line 554, in create
instance = self.create_one(commit=commit, **kwargs)
File "/Users/evanma/anaconda/lib/python2.7/site-packages/autofixture/base.py", line 519, in create_one
instance.save()
File "/Users/evanma/anaconda/lib/python2.7/site-packages/django/db/models/base.py", line 807, in save
force_update=force_update, update_fields=update_fields)
File "/Users/evanma/anaconda/lib/python2.7/site-packages/django/db/models/base.py", line 837, in save_base
updated = self._save_table(raw, cls, force_insert, force_update, using, update_fields)
File "/Users/evanma/anaconda/lib/python2.7/site-packages/django/db/models/base.py", line 923, in _save_table
result = self._do_insert(cls._base_manager, using, fields, update_pk, raw)
File "/Users/evanma/anaconda/lib/python2.7/site-packages/django/db/models/base.py", line 962, in _do_insert
using=using, raw=raw)
File "/Users/evanma/anaconda/lib/python2.7/site-packages/django/db/models/manager.py", line 85, in manager_method
return getattr(self.get_queryset(), name)(*args, **kwargs)
File "/Users/evanma/anaconda/lib/python2.7/site-packages/django/db/models/query.py", line 1076, in _insert
return query.get_compiler(using=using).execute_sql(return_id)
File "/Users/evanma/anaconda/lib/python2.7/site-packages/django/db/models/sql/compiler.py", line 1099, in execute_sql
cursor.execute(sql, params)
File "/Users/evanma/anaconda/lib/python2.7/site-packages/django/db/backends/utils.py", line 80, in execute
return super(CursorDebugWrapper, self).execute(sql, params)
File "/Users/evanma/anaconda/lib/python2.7/site-packages/django/db/backends/utils.py", line 65, in execute
return self.cursor.execute(sql, params)
File "/Users/evanma/anaconda/lib/python2.7/site-packages/django/db/utils.py", line 94, in __exit__
six.reraise(dj_exc_type, dj_exc_value, traceback)
File "/Users/evanma/anaconda/lib/python2.7/site-packages/django/db/backends/utils.py", line 65, in execute
return self.cursor.execute(sql, params)
django.db.utils.ProgrammingError: column "user_id" of relation "divexplorer_simulation" does not exist
LINE 1: INSERT INTO "divexplorer_simulation" ("user_id", "date", "hi...
I have spent hours trying to work through this error but to no avail. Any ideas?
I have tried renaming the argument db_column in the ForeignKey function, applying default values, but none of them work. Would appreciate some input thank you very much!

I believe you need to specify if related models should also be created with random values.
Please check the docs: http://django-autofixture.readthedocs.io/en/latest/loadtestdata.html
Where it is stated:
There are a few command line options available. Mainly to control the behavior of related fields. If foreingkey or many to many fields should be populated with existing data or if the related models are also generated on the fly. Please have a look at the help page of the command for more information:
django-admin.py help loadtestdata
Unfortunately I can't check a running instance of Django know in order to point you to the exact option and it's value but checking the docs I would say that you have to use this option from loadtestdata:
...
make_option('--generate-fk', action='store', dest='generate_fk', default=None,
help=u'Do not use already existing instances for ForeignKey relations. ' +
'Create new instances instead. You can specify a comma sperated list of ' +
'field names or ALL to indicate that all foreignkeys should be generated ' +
'automatically.'),
...

Django Models Relations to User Model

I'm new to the forum and I've got a problem.
in Django im trying to create a UserProfile class by referencing it via a OnetoOneField to an User Object. When i try to migrate, I get:
"You are trying to add a non-nullable field 'id' to author without a default; we can't do that (the database needs something to populate existing rows).
Please select a fix:
1) Provide a one-off default now (will be set on all existing rows)
2) Quit, and let me add a default in models.py"
I understand, that there are some fields in the User model (for example "id") that are not allowed to be null.
When I try to set a default it will makemigrations, but migrate fails with a syntax error.
My Question is how do I allow Null, or set a default that works, without writing a custom User class, and is that even possible ?
I'd really appreciate any help with this.
Here is my Code:
from django.db import models
from django.contrib.auth.models import User as User_django
class User(User_django):
pass
class Author(models.Model):
user = models.OneToOneField(User, null=True)
class BaseElement(models.Model):
author=models.ForeignKey(Author, null=True)
upvotes = models.PositiveIntegerField(default=0)
downvotes = models.PositiveIntegerField(default=0)
created = models.DateTimeField(auto_now_add=True, null=True)
def vote_up(self):
self.upvotes.value = self.upvotes.value + 1
def vote_down(self):
self.downvotes.value = self.downvotes.value + 1
class Meta:
abstract = True
class Post(BaseElement):
content = models.TextField(max_length=240)
tags = models.CharField(max_length=40, blank=True)
said_by = models.CharField(max_length=40)
said_at = models.CharField(max_length=40, blank=True)
def get_comments(self):
return self.comment_set.all()
def get_comments_anzahl(self):
return self.comment_set.all().count()
class Comment(BaseElement):
content = models.TextField(max_length=140)
commented_post = models.ForeignKey(Post, related_query_name="comment", null=True)
EDIT:
This happens if I try to set a default and try to migrate:
You are trying to add a non-nullable field 'id' to author without a
default; we can't do that (the database needs something to populate
existing rows).
Please select a fix:
1) Provide a one-off default now (will be set on all existing rows)
2) Quit, and let me add a default in models.py
Select an option: 1
Please enter the default value now, as valid Python
The datetime and django.utils.timezone modules are available, so you can
do e.g. timezone.now()
>>> 1
Migrations for 'post':
0003_auto_20160505_1237.py:
- Change Meta options on author
- Change managers on author
- Remove field user_ptr from author
- Add field id to author
- Add field user to author
Operations to perform:
Apply all migrations: contenttypes, admin, sessions, post, auth
Running migrations:
Rendering model states... DONE
Applying post.0003_auto_20160505_1237...Traceback (most recent call last):
File "/home/jaidmin/.conda/envs/cyf/lib/python3.5/site-packages/django/db/backends/utils.py", line 64, in execute
return self.cursor.execute(sql, params)
File "/home/jaidmin/.conda/envs/cyf/lib/python3.5/site-packages/django/db/backends/sqlite3/base.py", line 323, in execute
return Database.Cursor.execute(self, query, params)
sqlite3.OperationalError: near ")": syntax error
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "manage.py", line 10, in <module>
execute_from_command_line(sys.argv)
File "/home/jaidmin/.conda/envs/cyf/lib/python3.5/site-packages/django /core/management/__init__.py", line 353, in execute_from_command_line
utility.execute()
File "/home/jaidmin/.conda/envs/cyf/lib/python3.5/site-packages/django/core/management/__init__.py", line 345, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/home/jaidmin/.conda/envs/cyf/lib/python3.5/site-packages/django/core/management/base.py", line 348, in run_from_argv
self.execute(*args, **cmd_options)
File "/home/jaidmin/.conda/envs/cyf/lib/python3.5/site-packages/django/core/management/base.py", line 399, in execute
output = self.handle(*args, **options)
File "/home/jaidmin/.conda/envs/cyf/lib/python3.5/site-packages/django/core/management/commands/migrate.py", line 200, in handle
executor.migrate(targets, plan, fake=fake, fake_initial=fake_initial)
File "/home/jaidmin/.conda/envs/cyf/lib/python3.5/site-packages/django/db/migrations/executor.py", line 92, in migrate
self._migrate_all_forwards(plan, full_plan, fake=fake, fake_initial=fake_initial)
File "/home/jaidmin/.conda/envs/cyf/lib/python3.5/site-packages/django/db/migrations/executor.py", line 121, in _migrate_all_forwards
state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial)
File "/home/jaidmin/.conda/envs/cyf/lib/python3.5/site-packages/django/db/migrations/executor.py", line 198, in apply_migration
state = migration.apply(state, schema_editor)
File "/home/jaidmin/.conda/envs/cyf/lib/python3.5/site-packages/django/db/migrations/migration.py", line 123, in apply
operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
File "/home/jaidmin/.conda/envs/cyf/lib/python3.5/site-packages/django/db/migrations/operations/fields.py", line 121, in database_forwards
schema_editor.remove_field(from_model, from_model._meta.get_field(self.name))
File "/home/jaidmin/.conda/envs/cyf/lib/python3.5/site-packages/django/db/backends/sqlite3/schema.py", line 247, in remove_field
self._remake_table(model, delete_fields=[field])
File "/home/jaidmin/.conda/envs/cyf/lib/python3.5/site-packages/django/db/backends/sqlite3/schema.py", line 197, in _remake_table
self.quote_name(model._meta.db_table),
File "/home/jaidmin/.conda/envs/cyf/lib/python3.5/site-packages/django/db/backends/base/schema.py", line 110, in execute
cursor.execute(sql, params)
File "/home/jaidmin/.conda/envs/cyf/lib/python3.5/site-packages/django/db/backends/utils.py", line 79, in execute
return super(CursorDebugWrapper, self).execute(sql, params)
File "/home/jaidmin/.conda/envs/cyf/lib/python3.5/site-packages/django/db/backends/utils.py", line 64, in execute
return self.cursor.execute(sql, params)
File "/home/jaidmin/.conda/envs/cyf/lib/python3.5/site-packages/django/db/utils.py", line 95, in __exit__
six.reraise(dj_exc_type, dj_exc_value, traceback)
File "/home/jaidmin/.conda/envs/cyf/lib/python3.5/site-packages/django/utils/six.py", line 685, in reraise
raise value.with_traceback(tb)
File "/home/jaidmin/.conda/envs/cyf/lib/python3.5/site-packages/django/db/backends/utils.py", line 64, in execute
return self.cursor.execute(sql, params)
File "/home/jaidmin/.conda/envs/cyf/lib/python3.5/site-packages/django/db/backends/sqlite3/base.py", line 323, in execute
return Database.Cursor.execute(self, query, params)
django.db.utils.OperationalError: near ")": syntax error
EDIT:
It seems like I solved it by creating a new project and step by step copying the models and migrating. Still wondering what was going on there, because I flushed the database and deleted the migration files multiple times and it was still throwing errors.
Thanks for the help !

Take a look at this:
https://docs.djangoproject.com/es/1.9/topics/db/examples/one_to_one/
Your code is a ONE-to-ONE with user. When you set it, it implies CASCADE delete, and therefore can never be null.
if you change to One-to-Many, and just ensure that you only insert one object for the foreign key, it'll work. Otherwise, change your cascade rule.
I will say, however, that's not a good idea, because if you make it null, what separates it from other records. Consider a second PK field.
Best of luck.

Just import django's built-in User model like this:
from django.contrib.auth.models import User
and delete this line:
class User(User_django):
pass
from your code as it is completely unnecessary.
UPDATE: Also it looks like your problem has nothing to do with the User model. I think somehow you added an id field to your Author model and deleted it (maybe after an unsuccessful migration). If this is the case, then you could edit your 0003_auto_20160505_1237.py. To do that open it and remove the lines which look something like this:
migrations.AddField(
model_name='author',
name='id',
field=models.someFieldType(options)),
),
and try again.

Unknown column '' in 'field list'. Django

I'm using Django 1.9 and MySQL. I want to rename a field in my model. Let's look at model Choice from the Django getting started tutorial.
class Choice(models.Model):
question = models.ForeignKey(Question)
choice_text = models.CharField(max_length = 200)
votes = models.IntegerField(default=0)
So, I want to rename the votes field to votes_count. I created an empty migration and add to operations following line:
migrations.RenameField (
model_name='choice',
old_name='votes',
new_name='votes_count',
),
After python manage.py migrate, the field in the database table was renamed. But when I tried to use this model
def vote(request, question_id):
question = get_object_or_404(Question, pk=question_id);
try:
selected = question.choice_set.get(pk=request.POST['choice'])
except (KeyError, Choice.DoesNotExist):
return render(request, 'polls/detail.html', {
'question':question,
'error_message':"You didn't select a choice."
})
else:
selected.votes_count += 1
selected.save()
return HttpResponseRedirect(reverse('polls:results', args=(question_id)))
I got:
Unknown column 'polls_choice.votes' in 'field list
Traceback:
File "/home/verdigo/venv/lib/python3.4/site-packages/django/db/backends/utils.py" in execute
64. return self.cursor.execute(sql, params)
File "/home/verdigo/venv/lib/python3.4/site-packages/django/db/backends/mysql/base.py" in execute
112. return self.cursor.execute(query, args)
File "/home/verdigo/venv/lib/python3.4/site-packages/MySQLdb/cursors.py" in execute
226. self.errorhandler(self, exc, value)
File "/home/verdigo/venv/lib/python3.4/site-packages/MySQLdb/connections.py" in defaulterrorhandler
36. raise errorvalue
File "/home/verdigo/venv/lib/python3.4/site-packages/MySQLdb/cursors.py" in execute
217. res = self._query(query)
File "/home/verdigo/venv/lib/python3.4/site-packages/MySQLdb/cursors.py" in
_query
378. rowcount = self._do_query(q)
File "/home/verdigo/venv/lib/python3.4/site-packages/MySQLdb/cursors.py" in
_do_query
341. db.query(q)
File "/home/verdigo/venv/lib/python3.4/site-packages/MySQLdb/connections.py" in query
280. _mysql.connection.query(self, query)
The above exception ((1054, "Unknown column 'polls_choice.votes' in 'field list'")) was the direct cause of the following exception:
File "/home/verdigo/venv/lib/python3.4/site-packages/django/core/handlers/base.py" in get_response
149. response = self.process_exception_by_middleware(e, request)
File "/home/verdigo/venv/lib/python3.4/site-packages/django/core/handlers/base.py" in get_response
147. response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "./polls/views.py" in vote
23. selected = question.choice_set.get(pk=request.POST['choice'])
File "/home/verdigo/venv/lib/python3.4/site-packages/django/db/models/manager.py" in manager_method
122. return getattr(self.get_queryset(), name)(*args, **kwargs)
File "/home/verdigo/venv/lib/python3.4/site-packages/django/db/models/query.py" in get
381. num = len(clone)
File "/home/verdigo/venv/lib/python3.4/site-packages/django/db/models/query.py" in __len__
240. self._fetch_all()
File "/home/verdigo/venv/lib/python3.4/site-packages/django/db/models/query.py" in _fetch_all
1074. self._result_cache = list(self.iterator())
File "/home/verdigo/venv/lib/python3.4/site-packages/django/db/models/query.py" in __iter__
52. results = compiler.execute_sql()
File "/home/verdigo/venv/lib/python3.4/site-packages/django/db/models/sql/compiler.py" in execute_sql
848. cursor.execute(sql, params)
File "/home/verdigo/venv/lib/python3.4/site-packages/django/db/backends/utils.py" in execute
79. return super(CursorDebugWrapper, self).execute(sql, params)
File "/home/verdigo/venv/lib/python3.4/site-packages/django/db/backends/utils.py" in execute
64. return self.cursor.execute(sql, params)
File "/home/verdigo/venv/lib/python3.4/site-packages/django/db/utils.py" in
__exit__
95. six.reraise(dj_exc_type, dj_exc_value, traceback)
File "/home/verdigo/venv/lib/python3.4/site-packages/django/utils/six.py" in reraise
685. raise value.with_traceback(tb)
File "/home/verdigo/venv/lib/python3.4/site-packages/django/db/backends/utils.py" in execute
64. return self.cursor.execute(sql, params)
File "/home/verdigo/venv/lib/python3.4/site-packages/django/db/backends/mysql/base.py" in execute
112. return self.cursor.execute(query, args)
File "/home/verdigo/venv/lib/python3.4/site-packages/MySQLdb/cursors.py" in execute
226. self.errorhandler(self, exc, value)
File "/home/verdigo/venv/lib/python3.4/site-packages/MySQLdb/connections.py" in defaulterrorhandler
36. raise errorvalue
File "/home/verdigo/venv/lib/python3.4/site-packages/MySQLdb/cursors.py" in execute
217. res = self._query(query)
File "/home/verdigo/venv/lib/python3.4/site-packages/MySQLdb/cursors.py" in
_query
378. rowcount = self._do_query(q)
File "/home/verdigo/venv/lib/python3.4/site-packages/MySQLdb/cursors.py" in
_do_query
341. db.query(q)
File "/home/verdigo/venv/lib/python3.4/site-packages/MySQLdb/connections.py" in query
280. _mysql.connection.query(self, query)
Exception Type: OperationalError at /polls/1/vote/
Exception Value: (1054, "Unknown column 'polls_choice.votes' in 'field list'")

It looks as if you created and ran a migration to rename the model field from votes to votes_count, but did not update the model at the same time.
When the Django tries to fetch the model from the db, it tries to select the votes column because you still have a votes field in your models, and you get the error because the column doesn't exist in the database.
Creating a manual migration isn't normally necessary. Usually, you would rename the model field, run makemigrations, then run migrate. The advantage of letting Django create the migration is that you can be confident that the database is in sync with your models after you have run migrate.

Cause: This error occurs when a new one-to-many foreign key is created, pointing to the model with the forkey field and then generating the table
.
Solution: This problem can be solved by directly deleting the database and rebuilding it.
1: drop database database table;
2, re-create after deletion, before the code created, run directly

This is an issue that has persisted with me and lead me down a lot of rabbit holes dropping tables etc. A simple solution I have found is answering "N" when django asks you if you are renaming a field of that model (when running makemigrations). What that then essentially performs is a deletion of your previous field and creates the new field. Be careful as you may lose data on existing field so this works with fields which are either new or relatively easy to 'refill' their data required. You may need to run --fake if you get an error with regards to not being able to 'drop field' when migrating after makemigrations.
Update:
I did the above for a Boolean field and my data was kept. Even though I said N, it seems as if it is essentially a renaming.

Django Db Utils IntegrityError: (1062, "Duplicate entry '' for key 'slug'") [duplicate]

I'm trying to follow the tangowithdjango book and must add a slug to update the category table. However I'm getting an error after trying to migrate the databases.
http://www.tangowithdjango.com/book17/chapters/models_templates.html#creating-a-details-page
I didn't provide a default value for the slug, so Django asked me to provide one and as the book instructed I type in ''.
It's worth noticing that instead of using sqlite as in the original book I'm using mysql.
models.py
from django.db import models
from django.template.defaultfilters import slugify
# Create your models here.
class Category(models.Model):
name = models.CharField(max_length=128, unique=True)
views = models.IntegerField(default=0)
likes = models.IntegerField(default=0)
slug = models.SlugField(unique=True)
def save(self, *args, **kwargs):
self.slug = slugify(self.name)
super(Category, self).save(*args, **kwargs)
class Meta:
verbose_name_plural = "Categories"
def __unicode__(self):
return self.name
class Page(models.Model):
category = models.ForeignKey(Category)
title = models.CharField(max_length=128)
url = models.URLField()
views = models.IntegerField(default=0)
def __unicode__(self):
return self.title
The command prompt
sudo python manage.py migrate
Operations to perform:
Apply all migrations: admin, rango, contenttypes, auth, sessions
Running migrations:
Applying rango.0003_category_slug...Traceback (most recent call last):
File "manage.py", line 10, in <module>
execute_from_command_line(sys.argv)
File "/usr/local/lib/python2.7/dist-packages/django/core/management/__init__.py", line 385, in execute_from_command_line
utility.execute()
File "/usr/local/lib/python2.7/dist-packages/django/core/management/__init__.py", line 377, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/usr/local/lib/python2.7/dist-packages/django/core/management/base.py", line 288, in run_from_argv
self.execute(*args, **options.__dict__)
File "/usr/local/lib/python2.7/dist-packages/django/core/management/base.py", line 338, in execute
output = self.handle(*args, **options)
File "/usr/local/lib/python2.7/dist-packages/django/core/management/commands/migrate.py", line 160, in handle
executor.migrate(targets, plan, fake=options.get("fake", False))
File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/executor.py", line 63, in migrate
self.apply_migration(migration, fake=fake)
File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/executor.py", line 97, in apply_migration
migration.apply(project_state, schema_editor)
File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/migration.py", line 107, in apply
operation.database_forwards(self.app_label, schema_editor, project_state, new_state)
File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/operations/fields.py", line 37, in database_forwards
field,
File "/usr/local/lib/python2.7/dist-packages/django/db/backends/mysql/schema.py", line 42, in add_field
super(DatabaseSchemaEditor, self).add_field(model, field)
File "/usr/local/lib/python2.7/dist-packages/django/db/backends/schema.py", line 411, in add_field
self.execute(sql, params)
File "/usr/local/lib/python2.7/dist-packages/django/db/backends/schema.py", line 98, in execute
cursor.execute(sql, params)
File "/usr/local/lib/python2.7/dist-packages/django/db/backends/utils.py", line 81, in execute
return super(CursorDebugWrapper, self).execute(sql, params)
File "/usr/local/lib/python2.7/dist-packages/django/db/backends/utils.py", line 65, in execute
return self.cursor.execute(sql, params)
File "/usr/local/lib/python2.7/dist-packages/django/db/utils.py", line 94, in __exit__
six.reraise(dj_exc_type, dj_exc_value, traceback)
File "/usr/local/lib/python2.7/dist-packages/django/db/backends/utils.py", line 65, in execute
return self.cursor.execute(sql, params)
File "/usr/local/lib/python2.7/dist-packages/django/db/backends/mysql/base.py", line 128, in execute
return self.cursor.execute(query, args)
File "/usr/local/lib/python2.7/dist-packages/MySQLdb/cursors.py", line 205, in execute
self.errorhandler(self, exc, value)
File "/usr/local/lib/python2.7/dist-packages/MySQLdb/connections.py", line 36, in defaulterrorhandler
raise errorclass, errorvalue
django.db.utils.IntegrityError: (1062, "Duplicate entry '' for key 'slug'")

Let's analyse it step by step:
You're adding slug field with unique = True, that means: each record must have different value, there can't be two records with same value in slug
You're creating migration: django asks you for default value for fields that exists already in database, so you provided '' (empty string) as that value.
Now django is trying to migrate your database. In database we have at least 2 records
First record is migrated, slug column is populated with empty string. That's good because no other record is having empty string in slug field
Second record is migrated, slug column is populated with empty string. That fails, because first record already have empty string in slug field. Exception is raised and migration is aborted.
That's why your migration fails. All you should do is to edit migration, copy migrations.AlterField operation twice, in first operation remove unique=True. Between that operations you should put migrations.RunPython operation and provide 2 parameters into that: generate_slugs and migrations.RunPython.noop.
Now you must create inside your migration function BEFORE migration class, name that function generate_slugs. Function should take 2 arguments: apps and schema_editor. In your function put at first line:
Category = apps.get_model('your_app_name', 'Category')
and now use Category.objects.all() to loop all your records and provide unique slug for each of them.

If you have more than one category in your table, then you cannot have unique=True and default='', because then you will have more than one category with slug=''. If your tutorial says to do this, then it's bad advice, although it might work in SQLite.
The correct approach to add a unique field to a model is:
Delete your current migration that isn't working.
Add the slug field, with unique=False. Create a new migration and run it.
Set a unique slug for every category. It sounds like the rango populate script might do this. Alternatively, you could write a migration to set the slugs, or even set them manually in the Django admin.
Change the slug field to unique=True. Create a new migration and run it.
If that's too difficult, then you could delete all your categories from your database except one. Then your current migration will run without having problems with the unique constraint. You can add the categories again afterwards.

You must have rows in your table already with empty slugs, which is a violation of the mysql unique constraint you created. You can update them manually by running manage.py dbshell to get to the mysql client, then updating the offending rows, e.g.
update table rango_category set slug = name where slug = '';
(assuming the rows with blank slugs have names). Or you can delete the rows with
delete from rango_category where slug = '';
After that, you should be able to run your migrations.