Why Do Multiple Records Exist?

Multiple problems with your application can arise from duplicate records. First, they can confuse your users by showing them many entries for what they once believed to be a single item. Additionally, this may make it challenging to manage data and produce reliable reports. Additionally, since duplicate records occupy unneeded space in your database, they can affect speed.

Find Duplicate Records Using Django ORM

Fortunately, Django ORM has a number of methods for locating and eliminating duplicate data. Let’s look at some of the methods you have at your disposal.

Find Duplicate Records in a Single Field

Using the values() and annotate() methods to group records by a single field and count the number of records in each group is one technique to check for duplicates. For instance, if your Users model has a username field, you can use the following code to discover duplicate usernames.

#Checking Duplicate Record in Signle Field
@api_view(['GET',])
def GetduplicateUsers(request):
    if request.method == 'GET':
        getusers = authentication.objects.values('username','password').annotate(username_count=Count('username')).filter(username_count__gt=1)
        serializer = serialize(getusers, many=True)        
        return Response(serializer.data)

This code counts the number of records in each group of Users records and sorts them according to username . When there are duplicate records, the filter() method only returns the groups that have more than one record.

Finding Duplicates in Multiple Fields

Use the Q object and distinct() function to search for duplicate records across several fields. For instance, the following code may be used to discover duplicate records based on all two columns in a Users model with username and email fields:

#Checking Duplicate Record in multiple Field
@api_view(['GET',])
def GetduplicatemultipleUsers(request):
    if request.method == 'GET':
        getusers = authentication.objects.filter(Q(username__in=authentication.objects.values('username').annotate(count=Count('id')).filter(count__gt=1).values('username')) & Q(emailid__in=authentication.objects.values('emailid').annotate(count=Count('id')).filter(count__gt=1).values('emailid'))).distinct()
        serializer = serialize(getusers, many=True)        
        return Response(serializer.data)

The Q object is used in this code to filter Users’ records based on various fields. Records are grouped by each field using the values() and annotate() methods, and the number of records in each group is counted. Then, only the groups with multiple records, indicating that there are duplicates, are returned using the filter() method. Any duplicates are eliminated from the final query result using the distinct() technique.

Conclusion

In Django ORM, duplicate records can be an irritating and time-consuming issue. But with the methods described in this article, you may easily find and get rid of duplicates from your database. To maintain correct and clean data, keep in mind to periodically check for duplication.

The post How to Find Duplicate Records in Django ORM appeared first on Tech Insights.

Django Object Relational Mapping(ORM), makes this process easier by allowing you to work with Python classes instead of SQL queries.

Joining two or more tables to extract relevant data is one of the most common tasks when working with a database. We will look into joining tables with Django ORM in this tutorial.

Database Relationships

Before we dig into joining tables, it is essential to understand the different types of relationships that can exist between tables in a database. The three most common types of relationships are.

• One-to-one(1:1)  – Each record in one table is related to one and only one record in another table.
• One-to-many(1:N) – Each record in one table is related to zero, one, or many records in another table.
• Many-to-Many(N: N) – Each record in one table is related to zero, one, or many records in another table and vice versa.

Create Django Join

Create a Project

First, we need to create a project by running the following commands in your terminal or command prompt

Django-admin startproject Joins_ORM

Create an app

A Django project consists of one or more apps. Creating a new app by running the following command in your terminal or command prompt

Python manage.py startapp jointable

Create a Model

from django.db import models

# Create your models here.

class Author(models.Model):
    FirstName = models.CharField(max_length=100)
    LastName = models.CharField(max_length=100)
    MiddleName = models.CharField(max_length=100)

class Books(models.Model):
    title = models.CharField(max_length=200)
    total_page = models.IntegerField()
    auth_id = models.ForeignKey(Author, on_delete=models. CASCADE)
    

Django Join Tables Using ORM

INNER JOIN

from django.shortcuts import render
from .models import Books,Author

# Create your views here.

def jointable(request):
    books = Books.objects.select_related('auth_id').filter(title='A Better World')

    return render(request,'index.html',{'context':books})

LEFT JOIN

def Leftjoin(request):

    books = Books.objects.filter(Q(auth_id__isnull=True)|Q(auth_id__isnull=False))   
    return render(request,'index.html',{'context':books})

RIGHT JOIN

def Rightjoin(request):

    books = Books.objects.select_related('auth_id').all()

    return render(request,'index.html',{'context':books})

See More How to Add Pagination

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