This is part of the series Django For Beginners we are going to see about apps in app and we will see about models in django in this part.
In this post we are going to learn a lot queries in django. I recommend you to read last post so as it will be easy to understand context of this post , now let's get started.
These are the models which we are going to use for most part in this post,
from django.db import models
from django.utils import timezone
from djnago.contrib.auth.models import User
class Post(models.Model)
title = models.CharField(max_length=250)
created_at = models.DateTimeField(default=timezone.now)
author = models.ForeignKey('Author', on_delete=models.CASCADE, related_name="author")
likes = models.ManyToManyField(User, blank=True, related_name="likes")
dislikes = models.ManyToManyField(User, blank=True, related_name="dislikes")
likes_count = models.PositiveIntegerField(default=0)
dislikes_count = models.PositiveIntegerField(default=0)
rating = models.DecimalField(max_digits=4, decimal_places=2)
class Author(models.Model):
user = models.OneToOneField(User, on_delete=models.CASCADE)
liked_posts = models.ManyToManyField(Post, blank=True, related_name="liked_posts")
disliked_posts = models.ManyToManyField(Post, blank=True, related_name="disliked_posts")
Get All
To get all data of the model we use this query, it is not used most often as it costs a lot of resources if data is large and it is always a good practice to limit the query results which we will see how to do after this,
all_posts = Post.objects.all()
syntax = ModelName.objects.all()
Limit Query Results
To limit results of any query we add [ start_count : end_count ] to get results from start_count and end_count you can also use [ : end_count ] to get results from 0 to end_count. Let's see an example,
only_five_posts = Post.objects.all()[:4]
The above query will give 5 results only as index start from 0 and till 4 it would be five results.
Get Query
There is situation many times when we want to retrieve only one result from the query with exact match of fields for such situations we use get query, let me show you an example,
one_post = Post.objects.get(id=1)
syntax = ModelName.objects.get( pass_keyword_arguments )
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Top comments (2)
Very useful 💙
Thank You.