You need to figure out the number of the migration _just before_ the one you want to roll back.

Your app should have a migrations directory, with files in it named like

    0000_initial.py
    0001_added_some_fields.py
    0002_added_some_more_fields.py
    0003_deleted_some_stuff.py

Normally, when you run &lt;code&gt;./manage.py migrate your_app&lt;/code&gt;, South runs all new migrations, in order. (It looks at the database tables to decide which ones are &#39;new&#39;).

However, you can also specify any migration by number, and South will migrate your database, *either forward or backward*, to take it to that point. So, with the example files above, if you have already migrated up to 0003, and you wanted to run 0003 in reverse (undoing it, effectively), you would run

    ./manage.py migrate your_app 0002

South would look at the database, realise that it has run 0003 already, and determine that it has to run the reverse migration for 0003 in order to get back to 0002.

Just in case someone (like me) wondered how to **migrate back from initial (0001)**:

    django-admin.py migrate some_app zero

output:

    Running migrations for some_app:
     - Migrating backwards to zero state.
     &lt; some_app:0001_initial

&quot;zero&quot; is a special state before any migration.

Reference: http://south.aeracode.org/docs/commands.html

Add a migration name at the end of the parameters:

    ./manage.py migrate app-name 00xx-migration-name



I am trying to generate a random password in php. 

However I am getting all &#39;a&#39;s and the return type is of type array and I would like it to be a string. Any ideas on how to correct the code?

Thanks.

    function randomPassword() {
        $alphabet = &quot;abcdefghijklmnopqrstuwxyzABCDEFGHIJKLMNOPQRSTUWXYZ0123456789&quot;;
        for ($i = 0; $i &lt; 8; $i++) {
            $n = rand(0, count($alphabet)-1);
            $pass[$i] = $alphabet[$n];
        }
        return $pass;
    }

Generating a random password in php

How do I get the last character of a string?

    public class Main {
        public static void main(String[] args)  {
            String s = &quot;test string&quot;;
            //char lastChar = ???
        }   
    }


How do I get the last character of a string?

Ok, so this seems like a really silly thing to ask, and I&#39;m sure I&#39;m missing something somewhere.

How do you perform a backwards migration using South on Django?

So I&#39;ve tweaked my models, created a migration with `schemamigration`, run the migration with `migrate`, and now I realise that&#39;s not quite what I wanted and I want it back the way before.

Short of manually editing db tables and removing migration files, how should I go about rolling the migration back? I find references to backward migrations using South via Google, but have yet to find a solid code example for it.

Can anyone help?

Backwards migration with Django South

Ok, so this seems like a really silly thing to ask, and I'm sure I'm missing something somewhere.
How do you perform a backwards migration using South on Django?
So I've tweaked my models, created a migration with <code>schemamigration</code>, run the migration with <code>migrate</code>, and now I realise that's not quite what I wanted and I want it back the way before.
Short of manually editing db tables and removing migration files, how should I go about rolling the migration back? I find references to backward migrations using South via Google, but have yet to find a solid code example for it.
Can anyone help?

I would like to style the following:

**forms.py:**
   
    from django import forms

    class ContactForm(forms.Form):
	    subject = forms.CharField(max_length=100)
	    email = forms.EmailField(required=False)
	    message = forms.CharField(widget=forms.Textarea)

**contact_form.html:**

	&lt;form action=&quot;&quot; method=&quot;post&quot;&gt;
	  &lt;table&gt;
	    {{ form.as_table }}
	  &lt;/table&gt;
	  &lt;input type=&quot;submit&quot; value=&quot;Submit&quot;&gt;
	&lt;/form&gt;

For example, how do I set a **class** or **ID** for the `subject`, `email`, `message` to provide an external style sheet to?

CSS styling in Django forms

I am trying to limit access to pages using 2 user levels. Superuser and admin.
Super user is a regular Django user with &#39;is_superuser&#39; assigned.
Admin user is also a regular user with only the &#39;is_staff&#39; permission assigned.

The problem is that when i use this decorator for an admin user, it doesn&#39;t pass the test:

    @permission_required(&#39;is_staff&#39;)
    def my_view(....)

`@permission_required(&#39;is_staff&#39;)` returns false for anonymous users. (correct)  
`@permission_required(&#39;is_superuser&#39;)` only returns true for superusers (correct)  
`@permission_required(&#39;is_staff&#39;)` returns FALSE for users with the &#39;is_staff&#39; perm assigned. (wrong).

Any thoughts?

Django is_staff permission decorator

Am building an app using Django as my workhorse. All has been well so far - specified db settings, configured static directories, urls, views etc. But trouble started sneaking in the moment I wanted to render my own beautiful and custom 404.html and 500.html pages.

I read the docs on custom error handling, and set necessary configurations in UrlsConf, created corresponding views and added the 404.html and the 500.html to my app&#39;s template directory (specified in the settings.py too).

But the docs say `you can actually view custom error views until Debug is Off`, so I did turn it off to test my stuff, and that&#39;s when stuff goes berserk!

Not only do I fail to view the custom 404.html (actually, it loads, but because my error pages each contain a graphic error message -as some nice image), the source of the error page loads, but nothing else loads! Not even linked CSS or Javascript!

Generally, once I set `DEBUG = False`, all views will load, but any linked content (CSS, Javascript, Images, etc) wont load! What&#39;s happening? Is there something am missing, concerning static files and the `DEBUG` setting?

Why does DEBUG=False setting make my django Static Files Access fail?

What&#39;s the difference between Django `OneToOneField` and `ForeignKey`?

What&#39;s the difference between django OneToOneField and ForeignKey?

How can I subtract or add 100 years to a `datetime` field in the database in Django?

The date is in database, I just want to directly update the field without retrieving it out to calculate and then insert.

How can I subtract or add 100 years to a datetime field in the database in Django?

Very simple question here - if migrations can get slow and cumbersome as an app gets more complex and if we have the much cleaner `rake db:schema:load` to call instead, why do migrations exist at all?

If the answer to the above is that migrations are used for version control (a stepwise record of changes to the database), then as an app gets more complex and `rake db:schema:load` is used more instead, do they continue to maintain their primary function?

---

### Caution:

From the answers to this question: `rake db:schema:load` &lt;b&gt;will delete data&lt;/b&gt; on a production server so be careful when using it.

rake db:schema:load vs. migrations

I created a date column in a previous migration and set it to be nullable. Now I want to change it to be not nullable. How do I go about doing this assuming there are null rows in that database? I&#39;m ok with setting those columns to Time.now if they&#39;re currently null.

How to change a nullable column to not nullable in a Rails migration?

    rails generate migration AddRetweetsCountToTweet retweets_count:integer 
Ok I use above line to create migration file that automatically generates code in the generated file to add a column to a model Tweet with datatype integer. Now I want to add default value to the added column while generating the migration file. Is that possible? I googled it but couldn&#39;t find. Guys need help. 

Assigning default value while creating migration file

I am involved in a data migration project. I am getting the following error when I try to insert data from one table into another table (SQL Server 2005):

&gt; Msg 8152, Level 16, State 13, Line 1  
&gt; String or binary data would be truncated.

The source data columns match the data type and are within the length definitions of the destination table columns so I am at a loss as to what could be causing this error.


SQL Server String or binary data would be truncated

I have two models `restaurant` and `user` that I want to perform a has_and_belongs_to_many relationship.

I have already gone into the model files and added the `has_and_belongs_to_many :restaurants` and `has_and_belongs_to_many :users`

I assume at this point I should be able to do something like with Rails 3:

    rails generate migration ....

but everything I have tried seems to fail. I&#39;m sure this is something really simple I&#39;m new to rails so I&#39;m still learning.

Rails has_and_belongs_to_many migration

Can you migrate an app backwards to before its first migration in Django South? If not, are there plans to add such functionality, perhaps using an option passed to `migrate`?

Can you migrate backwards to before the first migration in South?

I have models in Django set up as below. 


    class Pupil(models.Model):
    	forename = models.CharField(max_length=30)
    	surname = models.CharField(max_length=30)
    	dateofbirth = models.DateField()
    	year = models.IntegerField()
    	class_group = models.CharField(max_length=30)
    	email = models.EmailField(blank=True)
    	assignments = models.ManyToManyField(&#39;Assignment&#39;, verbose_name=&#39;related assignments&#39;)
    
    	def __unicode__(self):
    		return u&#39;%s %s&#39; % (self.forename, self.surname)
    
    class Subject(models.Model):
    	name = models.CharField(max_length=30)
    	level = models.CharField(max_length=30)
    	teachers = models.ManyToManyField(&#39;Teacher&#39;, verbose_name=&#39;related teachers&#39;)
    
    	def __unicode__(self):
    		return self.name
    
    class Teacher(models.Model):
    	forename = models.CharField(max_length=30)
    	surname = models.CharField(max_length=30)
    	email = models.EmailField(blank=True)
    
    	def __unicode__(self):
    		return u&#39;%s %s&#39; % (self.forename, self.surname)
    
    class Assignment(models.Model):
    	assignment_name = models.CharField(max_length=30)
    	date_assigned = models.DateField()
    	date_submitted = models.DateField()
    
    	def __unicode__(self):
    		return self.assignment_name

When I attempt to add a pupil and attach an assignment to the pupil in the admin, I get a database error -  

    no such table: homework_pupil_assignments

after reading [this][1] I realised this could be due to django not updating changes to my models as when I do `manage.py sqlall homework`


I see the following:

    BEGIN;
    CREATE TABLE &quot;homework_pupil_assignments&quot; (
        &quot;id&quot; integer NOT NULL PRIMARY KEY,
        &quot;pupil_id&quot; integer NOT NULL,
        &quot;assignment_id&quot; integer NOT NULL,
        UNIQUE (&quot;pupil_id&quot;, &quot;assignment_id&quot;)
    )
    ;
    CREATE TABLE &quot;homework_pupil&quot; (
        &quot;id&quot; integer NOT NULL PRIMARY KEY,
        &quot;forename&quot; varchar(30) NOT NULL,
        &quot;surname&quot; varchar(30) NOT NULL,
        &quot;dateofbirth&quot; date NOT NULL,
        &quot;year&quot; integer NOT NULL,
        &quot;class_group&quot; varchar(30) NOT NULL,
        &quot;email&quot; varchar(75) NOT NULL
    )
    ;
    CREATE TABLE &quot;homework_subject_teachers&quot; (
        &quot;id&quot; integer NOT NULL PRIMARY KEY,
        &quot;subject_id&quot; integer NOT NULL,
        &quot;teacher_id&quot; integer NOT NULL,
        UNIQUE (&quot;subject_id&quot;, &quot;teacher_id&quot;)
    )
    ;
    CREATE TABLE &quot;homework_subject&quot; (
        &quot;id&quot; integer NOT NULL PRIMARY KEY,
        &quot;name&quot; varchar(30) NOT NULL,
        &quot;level&quot; varchar(30) NOT NULL
    )
    ;
    CREATE TABLE &quot;homework_teacher&quot; (
        &quot;id&quot; integer NOT NULL PRIMARY KEY,
        &quot;forename&quot; varchar(30) NOT NULL,
        &quot;surname&quot; varchar(30) NOT NULL,
        &quot;email&quot; varchar(75) NOT NULL
    )
    ;
    CREATE TABLE &quot;homework_assignment&quot; (
        &quot;id&quot; integer NOT NULL PRIMARY KEY,
        &quot;assignment_name&quot; varchar(30) NOT NULL,
        &quot;date_assigned&quot; date NOT NULL,
        &quot;date_submitted&quot; date NOT NULL
    )
    ;
    COMMIT;


I then installed South, following the directions to get up and running with an existing app, in the hope of successfully syncing these tables. No joy. 

Can anyone suggest how I can get the database (sqlite3) to reflect the models or point out what I&#39;m doing wrong?



  [1]: https://stackoverflow.com/questions/10077721/django-databaseerror-no-such-table

django no such table:

I am trying to apply a migration but am getting the error:

&gt; django.db.utils.OperationalError: (1050, &quot;Table &#39;customers_customer&#39;
&gt; already exists&quot;)

I get this by issuing the following command:

    python manage.py migrate

My customer table already exists, so what do I do to let the migration know this, not error out, and run my modification to my model?


I ran this on my local environment with local database with no problem.  It is when I pointed my database to production and ran `migrate` above that I get this error.

django 1.7 migrate gets error &quot;table already exists&quot;

(I know there is a title the same as this, but the question is different). 

I have managed to get my development machine migrations and production migrations out of sync. 

I have a Django app which was using South. I had my own workflow that worked fine (it probably wasn&#39;t the correct way to do things, but I had no problems with it). 

Basically I have a script that copies the production database dump to my development machine. It also copied the migration files. That way the two were in synch, and I could run South commands as normal. 


Now I have upgraded to 1.7, and started using migrations. When I use my previous workflow (copy database dump, and migration files from production), it is not detecting changes on my development machine.

I have read through the migrations document, and I see that the correct way to use it is to 

 1. run &quot;make migrations&quot; and &quot;migrate&quot; on my development machine.
 2. run &quot;migrate&quot; on my devlopemnt machine to actually make the database changes
 3. Copy changes over, including migration files.
 4. run &quot;migrate&quot; on the production machine. (without the &quot;makemigrations&quot; step)

Anyway. It is all a mess now. I would like to &quot;reset&quot; my migrations and start from scratch, doing things properly from now on.

What do I need to do? 

 1. Delete the contents of the migration table (on both machines)?
 2. Delete the contents of the migration folder? (Including the __init__.py file).  
 3. Start the migrations as per the documentation for a new one.

Have I missed anything?
Is there a reason why copying everything from production(database and migration files) doesn&#39;t detect any changes on my development machine afterwards

How to reset migrations in Django 1.7

According to the documentation here:
https://docs.djangoproject.com/en/1.8/topics/migrations/ it says:
    
    migrate, which is responsible for applying migrations, as well as unapplying and listing their status.

and

    makemigrations, which is responsible for creating new migrations based on the changes you have made to your models.

From what I understand, I first do

    makemigrations

to create the migration file and then do

    migrate

to actually apply the migration?

Do note though that I just began my Django project and I added my app to my &quot;installed_apps&quot; list. After that, I did

    python manage.py runserver

and it said 

    You have unapplied migrations; your app may not work properly until they are applied. Run &#39;python manage.py migrate&#39; to apply them.

It didn&#39;t mention anything about running makemigrations.


Content Type	Original Author	Original Content on Stackoverflow
Question	Ruiwen	View Question on Stackoverflow
Solution 1 - Django	Ian Clelland	View Answer on Stackoverflow
Solution 2 - Django	Ctrl-C	View Answer on Stackoverflow
Solution 3 - Django	Jerzyk	View Answer on Stackoverflow

Backwards migration with Django South

Django Problem Overview

Django Solutions

Solution 1 - Django

Solution 2 - Django

Solution 3 - Django

How do I get the last character of a string?

Generating a random password in php

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