Query Multiple Tables in Django and geta consolidated result-CodePudding

I am building a Blog application in Django and currently stuck at Querying the Data. I am creating a Post and then uploading multiple images to that post.

This is my Blog Post Model.

class Post(models.Model):
    user = models.ForeignKey(User, on_delete=models.PROTECT)
    title = models.CharField(max_length=255)   
    description = models.CharField(max_length=1000,null=True)
    Tags = models.CharField(max_length = 255,null=True,blank=True)
    Created_date = models.DateTimeField(auto_now_add=True)
    Updated_date = models.DateTimeField(auto_now=True)
    category = models.ForeignKey(Category, on_delete=models.PROTECT)

And this is my Images Model

class Images(models.Model):
    Post = models.ForeignKey(Post,on_delete=models.CASCADE)
    image = models.ImageField(upload_to='media/')

Now using this implementation I have 2 tables in DB in which data is stored as expected. In the first tables all the details related to Post are being stored and in the second Table ID, Post_Id, Image_URL is being stored. If I upload 3 images then three rows are being created.

Now I want to Query the data that is -> I want all the posts and I want all the Images according to the Posts.

I can get seprate queries for Post and Images but how can this be done in Django ORM? How can I query The data?

CodePudding user response：

You can use like this;

post = Post.objects.all().prefetch_related('images_set').get(pk=1)
images = post.images_set.all() # this will bring you all images related to 
                                post

CodePudding user response：

Assuming you have a view that populates a context variable named posts with a queryset like Post.objects.all() your template could look something like this simplified

{% for post in posts %}
    {{ post.title }}
    {{ post.category }}
    {{ post.description }}
    ...
    {% for image in post.images_set.all %}
         {{ image.image.url }}
    {% endfor %}
{% endfor %}

Every time you iterate over post.images_set.all you will execute another query, you should use prefetch_related so that you don't perform a query each time and the data is cached

    posts = Post.objects.prefetch_related('images_set')