Database query optimization with select_related in Django - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to fetch all books with their related authors efficiently.

Django

books = Book.objects.[1]('author')

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

Aannotate

Bfilter

Cexclude

Dselect_related

Attempts:

3 left

💡 Hint

Common Mistakes

Using filter instead of select_related causes multiple queries.

Using annotate or exclude does not fetch related objects efficiently.

Using select_related fetches related foreign key objects in one query, improving efficiency.

2fill in blank

medium

Complete the code to fetch all orders with their related customers using the best query optimization.

Django

orders = Order.objects.[1]('customer')

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

Aprefetch_related

Bvalues

Cselect_related

Daggregate

Attempts:

3 left

💡 Hint

Common Mistakes

Using prefetch_related causes extra queries for foreign keys.

Using values or aggregate does not fetch related objects.

select_related is best for single-valued relationships like foreign keys to fetch related objects in one query.

3fill in blank

hard

Fix the error in the code to optimize fetching books and their publishers in one query.

Django

books = Book.objects.[1]('publisher')

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

Aselect_related

Bprefetch_related

Conly

Ddefer

Attempts:

3 left

💡 Hint

Common Mistakes

Using prefetch_related causes multiple queries for foreign keys.

Using only or defer does not fetch related objects.

select_related is used to follow foreign key relationships and fetch related objects in one query.

4fill in blank

hard

Fill both blanks to create a dictionary of authors and their books, optimizing queries.

Django

author_books = {author.name: author.[1].all() for author in Author.objects.[2]('book_set')}

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

Abook_set

Bselect_related

Cprefetch_related

Dobjects

Attempts:

3 left

💡 Hint

Common Mistakes

Using select_related for reverse foreign keys causes errors.

Not using prefetch_related causes many queries.

Use prefetch_related to fetch reverse foreign key sets like book_set efficiently.

5fill in blank

hard

Fill all three blanks to create a dictionary of orders and their related customer names, optimizing queries.

Django

order_dict = {order.id: order.[1].[2] for order in Order.objects.[3]('customer')}

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

Acustomer

Bname

Cselect_related

Dcustomer_set

Attempts:

3 left

💡 Hint

Common Mistakes

Using customer_set instead of customer causes attribute errors.

Not using select_related causes many queries.

Use select_related to fetch the related customer object, then access its name attribute.