Aggregate and annotate methods in Django - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to calculate the total number of books in the database using Django's ORM.

Django

from django.db.models import [1]
total_books = Book.objects.aggregate({"total": [1]('id')})

Drag options to blanks, or click blank then click option'

AAvg

BSum

CCount

DMax

Attempts:

3 left

💡 Hint

Common Mistakes

Using Sum instead of Count causes an error because IDs are not summed.

Using Avg or Max does not count the number of books.

The Count function counts the number of records. Here, it counts all book IDs.

2fill in blank

medium

Complete the code to annotate each author with the number of books they have written.

Django

from django.db.models import [1]
authors = Author.objects.annotate(book_count=[1]('book'))

Drag options to blanks, or click blank then click option'

AAvg

BSum

CMax

DCount

Attempts:

3 left

💡 Hint

Common Mistakes

Using Sum instead of Count will not count related books.

Using Avg or Max is not suitable for counting.

The Count function counts related books per author.

3fill in blank

hard

Fix the error in the code to get the average price of all books.

Django

from django.db.models import [1]
avg_price = Book.objects.aggregate(avg_price=[1]('price'))

Drag options to blanks, or click blank then click option'

ACount

BAvg

CMax

DSum

Attempts:

3 left

💡 Hint

Common Mistakes

Using Count or Sum returns wrong results or errors.

Using Max returns the highest price, not the average.

The Avg function calculates the average value of the specified field.

4fill in blank

hard

Fill both blanks to annotate each book with the total number of pages and filter books with more than 300 pages.

Django

from django.db.models import [1]
books = Book.objects.annotate(total_pages=[1]('pages')).filter(total_pages__[2]=300)

Drag options to blanks, or click blank then click option'

ASum

BCount

Cgt

Dlt

Attempts:

3 left

💡 Hint

Common Mistakes

Using Count instead of Sum for pages.

Using lt (less than) instead of gt (greater than) in filter.

Sum adds up the pages, and gt means 'greater than' to filter books with more than 300 pages.

5fill in blank

hard

Fill all three blanks to annotate authors with the maximum book price, minimum book price, and average book price.

Django

from django.db.models import [1], [2], [3]
authors = Author.objects.annotate(max_price=[1]('book__price'), min_price=[2]('book__price'), avg_price=[3]('book__price'))

Drag options to blanks, or click blank then click option'

AMax

BMin

CAvg

DCount

Attempts:

3 left

💡 Hint

Common Mistakes

Using Count instead of Min or Max.

Mixing up the order of functions.

Max, Min, and Avg calculate the highest, lowest, and average book prices respectively.