This is the third blog of the series Everything About Django. In this article we are going to study about Models and Migrations.
What are Models?
- Models are the database tables.
- Django uses ORM (Object Relational Mapping) for models.
- Each model is a subclass inherited from
django.db.models.Model
class. - Every attribute in Django Model specifies a field in the database table.
What is ORM?
- ORM means Object Relational Mapper, one of the most powerful feature of Django.
- Django's ORM is just a pythonical way to create SQL to query and manipulate your database and get results in a pythonic fashion.
- How wonderful this is, you need not type SQL and do all the db stuff.
How to create a model?
Let's take an example to see how a model is made.
from django.db import models
class Student(models.Model):
name = models.CharField(max_length=100)
roll = models.IntegerField()
address = models.CharField(max_length=200)
This way I have created a table Student with the following attributes : name - Char, roll - Integer, address - Char.
In SQL we do this by :
CREATE TABLE Student
(
roll int,
name varchar(100),
address varchar(200)
);
So you see how easy and pythonic this is with Django.
What is a migration?
- Once we have defined a model, it's just a python code not yet reflected in our database, no table is created so far, until we migrate this to our database.
- Once our models is defined, we need to run
python manage.py makemigrations
. See the example bro. - Here core is the app in which my models is defined. It creates a folder in my app
migrations
. - With every makemigrations, a file is created like
0001_initial.py
which contains the information about our reflected changes in the database, which looks like this. This is a internal file created by django to reflect changes in the db. - Once we have made migrations, we need to actually reflect them in the database to create and modify the table. For this run,
python manage.py migrate
. This command will run the latest migrations made and reflect their changes.
I will create an article on tips while creating a model, where I will define all the attributes, functions one should define in a model.
THANK YOU
You can find me on : Priyanshu Panwar | LinkedIn
Please feel free to comment for any help or topic I should write an article on.
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