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Querying for values from several models


Querying for values from several models

By : Suyog Nagare
Date : November 21 2020, 04:01 AM
like below fixes the issue I have a Course and Lesson models. Course has several lessons. I want to find all the lessons for currently logged in student to generate kind of timetable.
code :
class Student < ApplicationRecord
  has_many :courses

  def active_lessions
    Lession.joins(course: :students).where(students: {id: self.id})
  end
end
current_student.active_lessions


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Querying through several models

Querying through several models


By : Benjamin Waters
Date : March 29 2020, 07:55 AM
fixed the issue. Will look into that further I don't think that it's a bad idea to query each model separately - indeed, from a database perspective, I can't see how you'd be able to do otherwise, as each model will need a separate SQL query. Even if, as @Nagaraj suggests, you set up a common Date model every other model references, you'd still need to query each model separately. You are probably correct, however, that putting the results into a list is bad practice, unless you actually need to load every object into memory, as explained here:
code :
querysets = [cls.objects.filter(date=now) for cls in [Model1, Model2, Model3]]
django querying from 3 models

django querying from 3 models


By : Karnakar Goud
Date : March 29 2020, 07:55 AM
hop of those help? First of all - python naming convention state that classes should not have underscores and prefer upper-case letters instead. So your models should be SourceEnquiry, Customer (not plural) and SaleCycle.
That being said, let's say I have a SourceEnquiry item (I'm going to pick one arbitrarily), and you want all related SaleCycle items, you do it like so:
code :
>>> sinq = SourceEnquiry.objects.get(pk=1)
>>> SaleCycle.objects.all().filter(customer_name__customer_src_n_type=sinq)
class Customer(models.Model):
    name = models.CharField(max_lentgth=200) 
    src_n_type = models.Foreign_key(source_of_enquiry)
    contact = models.CharField(max_lentgth=200)
class SourceEnquiry(models.Model):
    value = models.CharField(max_length=200, null=True, blank=True)

class SaleCycle(models.Model):
    item = models.CharField(max_length=200) 
    customer = models.Foreignkey(Customer)
Querying Models in Laravel

Querying Models in Laravel


By : user7656569
Date : March 29 2020, 07:55 AM
will help you I would like to be able to write an eloquent query that I could pass in to this model function to return only categories that have stories published on $publishDate. , relation:
code :
public function stories()
{      
    return $this->hasMany('Workbench\Dailies\Story', 'category_id');
}
// $publishedAt is some date you want

Category::whereHas('stories', function($query) use ($publishedAt) { 
    $query->where('published_at', '=', $publishedAt)->orderBy('story_title','asc'); 
})->orderBy('id','asc')->get();
Laravel 5.1 How to get all models and related models by querying a related model?

Laravel 5.1 How to get all models and related models by querying a related model?


By : help
Date : November 05 2020, 09:01 AM
Querying through four models in Rails

Querying through four models in Rails


By : Евгений Ветчанин
Date : March 29 2020, 07:55 AM
This might help you My relationships are set up like this: , Assuming
code :
class Audit
  belongs_to :content_body
end
class ContentBody
  belongs_to :document
end
class Document
  belongs_to :project
end 
@audits = Audit.joins(content_body: { document: :project })
            .where(projects: {id: some_id })
            .order(created_at: :desc) 
@audits = Audit.joins(content_body: :document)
            .where(documents: {project_id: some_id })
            .order(created_at: :desc)  
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