[Django]-Django 1.8 – what's the difference between migrate and makemigrations?

According the Polls tutorial:

1. python manage.py makemigrations <app>: Create the migrations (generate the SQL commands).

2. python manage.py migrate: Run the migrations (execute the SQL commands).

As Django’s documentation says migrations are Django’s way of propagating changes you make to your models (adding a field, deleting a model, etc.) into your database schema.

makemigrations basically generates the SQL commands for preinstalled apps (which can be viewed in installed apps in settings.py) and your newly created apps’ model which you add in installed apps.It does not execute those commands in your database file. So tables aren’t created after makemigrations.

After applying makemigrations you can see those SQL commands with sqlmigrate which shows all the SQL commands that have been generated by makemigrations.

migrate executes those SQL commands in database file. So after executing migrate, all the tables of your installed apps are created in your database file.

You can confirm this by installing sqlite browser and opening db.sqlite3 you can see all the tables appears in the database file after executing migrate command.

As we know Django is an ORM (Object Relational Mapping). When we use the command:

python manage.py makemigrations [app_name]

It will generate the sql command to create the table corresponding to each class you made in models.py file.
then the command:

python manage.py migrate [app_name]

will create the table in database using the commands which have been generated by makemigrations.

For example, if we make a model class-

from django.db import models

class Person(models.Model):
    first_name = models.CharField(max_length=30)
    last_name = models.CharField(max_length=30)

The corresponding sql command after using makemigrations will be

CREATE TABLE myapp_person (
"id" serial NOT NULL PRIMARY KEY,
"first_name" varchar(30) NOT NULL,
"last_name" varchar(30) NOT NULL
);

and using above command, table will be created in the database when we use migrate.

You should run the command -migrate- after adding a new app under the INSTALLED APPS section in the settings.py file in order to synchronize the database state with your current set of models. Assuming you’ve already modified the models.py file.

When you run -makemigrations- it packages up changes to your model into individual migration files.

Normally you would first run makemigrations and then migrate.

See documentation on Django Models

It is necessary to run both the commands to complete the migration of the database tables to be in sync with your models.

makemigrations simply analyzes your current models for any changes that would be out of sync with your database and creates a migrations file that can be used to bring the in sync. If left at this point, your models would still be out of sync with your database possibly breaking your code that queries the database.

migrate is the command to "Make It So!" and apply the changes noted during the makemigrations phase.

Source

Make migrations : Basically it generate SQL Commands for preinstalled apps and newly created app model which you added in installed app. It dose not executed SQL commands in your database. So actual tables are not created in DB.

Migrate : Migrate execute those SQL commands which are generated by make-migration in Database file . So after migrate all the tables of installed app are created in DB.

This is django’s replacement for the old manual south way of making migrations, they can be used to catalog changes in your models and write out changes that will take place in the db.

Migrate is basically the old syncdb but it takes into account all the migrations made by makemigrations.

makemigrations: creates the migrations (generating SQL Command- not yet executed)

migrate: run the migrations (executes the SQL command)

But in your case, Django is asking you to migrate the DEFAULT migrations which should run before first running of server. This would have been the same warning without even creating the first app.

According to the second tutorial of the django tutorial series. Migrations are:

The migrate command takes all the migrations that haven’t been applied (Django tracks which ones are applied using a special table in your database called django_migrations) and runs them against your database - essentially, synchronizing the changes you made to your models with the schema in the database.

So pretty much all it does is:

1. When you execute the make migrations command you’re saving the ‘instructions’ to mysql
2. When you execute the migrate command, you’re executing those same instructions