Search and ordering in Django - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output of this Django queryset ordering?

Given the model Book with fields title and published_date, what will be the order of titles returned by this queryset?

Book.objects.order_by('-published_date', 'title').values_list('title', flat=True)

Django

Assume the database has these books:<br>- 'Alpha' published 2020-01-01<br>- 'Beta' published 2021-01-01<br>- 'Gamma' published 2021-01-01

A ['Beta', 'Gamma', 'Alpha']

B ['Gamma', 'Beta', 'Alpha']

C ['Alpha', 'Beta', 'Gamma']

D ['Alpha', 'Gamma', 'Beta']

💡 Hint

Ordering first by published_date descending, then by title ascending.

The queryset orders books first by published_date descending, so 2021 books come first. Among those with the same date, titles are ordered ascending alphabetically. So 'Beta' comes before 'Gamma'.

📝 Syntax

intermediate

Which option correctly filters and orders a queryset by a search term in Django?

You want to find all Product objects whose name contains 'phone' (case-insensitive) and order them by price ascending. Which queryset is correct?

A Product.objects.filter(name__icontains='phone').order_by('-price')

B Product.objects.filter(name__contains='phone').order_by('-price')

C Product.objects.filter(name__icontains='phone').order_by('price')

D Product.objects.filter(name__contains='phone').order_by('price')

💡 Hint

Use case-insensitive contains and ascending order.

Option C uses icontains for case-insensitive search and orders by price ascending. Others either use case-sensitive filter or wrong order direction.

🔧 Debug

advanced

Why does this Django queryset raise a FieldError?

Consider this queryset:
Entry.objects.order_by('author__name')
Given Entry has a ForeignKey to Author model, why does this raise FieldError?

A Because ordering by related fields requires the related field to be in Meta.ordering

B Because ForeignKey fields cannot be used in order_by

C Because 'author__name' is a valid field and should not raise an error

D Because 'author__name' is not a valid field for ordering without using select_related()

💡 Hint

Ordering by related fields needs proper query setup.

Ordering by a related field like 'author__name' requires Django to join the related table. Without select_related(), Django may raise FieldError if the join is missing or ambiguous.

🧠 Conceptual

advanced

What is the effect of using distinct() after order_by() in a Django queryset?

Given a queryset:
MyModel.objects.order_by('category').distinct('category')
What does this do?

A Returns all records ordered by category, ignoring duplicates

B Returns one unique record per category, ordered by category ascending

C Raises a NotSupportedError because distinct with fields is not supported on all databases

D Returns records ordered by category but distinct() has no effect

💡 Hint

distinct() with fields returns unique rows by those fields.

Using distinct('category') returns one record per unique category, ordered by category ascending. However, this is only supported on PostgreSQL and may raise errors on other databases.

❓ state_output

expert

What is the output of this Django search and ordering code snippet?

Given the model Article with fields title and views, and these records:
- 'Django Tips', views=100
- 'Python Tricks', views=150
- 'Django Advanced', views=100

What does this code output?

qs = Article.objects.filter(title__icontains='django').order_by('-views', 'title').values_list('title', flat=True)
list(qs)

A ['Django Advanced', 'Django Tips']

B ['Django Tips', 'Django Advanced']

C ['Python Tricks', 'Django Tips', 'Django Advanced']

D ['Django Tips']

💡 Hint

Filter by 'django' in title, order by views descending, then title ascending.

Filter keeps 'Django Tips' and 'Django Advanced'. Both have 100 views, so ordering by -views keeps them equal, then title ascending orders 'Django Advanced' before 'Django Tips'.

Practice

1. What is the main purpose of adding search and ordering features in a Django ListView?

easy

A. To change the database schema automatically

B. To speed up the server response time

C. To disable pagination on the page

D. To let users find and sort data easily

Solution

1. Step 1: Understand the role of search and ordering

   Search and ordering help users locate specific data and arrange it in a preferred sequence.

2. Step 2: Identify the main benefit in a ListView context

   In Django ListView, these features improve user experience by making data easier to find and view in order.

3. Final Answer:

   To let users find and sort data easily -> Option D

4. Quick Check:

   Search and ordering = user-friendly data access [OK]

Hint: Search and ordering improve user data access quickly [OK]

Common Mistakes:

• Thinking search changes database structure
• Assuming ordering disables pagination
• Believing it speeds server without code changes

2. Which of the following is the correct way to override the get_queryset method in a Django ListView to add ordering by a field named name?

easy

A. def get_queryset(self): return self.queryset.order_by('name')

B. def get_queryset(self): return super().get_queryset().order_by('name')

C. def get_queryset(self): return self.objects.order_by('name')

D. def get_queryset(self): return Model.objects.order_by('name')

Solution

1. Step 1: Recall how to override get_queryset in ListView

   Use super() to get the base queryset, then apply ordering.

2. Step 2: Check each option for correct syntax and context

   def get_queryset(self): return super().get_queryset().order_by('name') correctly calls super() and orders by 'name'. Others misuse queryset or model references.

3. Final Answer:

   def get_queryset(self): return super().get_queryset().order_by('name') -> Option B

4. Quick Check:

   Use super() + order_by() = def get_queryset(self): return super().get_queryset().order_by('name') [OK]

Hint: Use super() to get base queryset before ordering [OK]

Common Mistakes:

• Using self.queryset without defining it
• Calling objects on self instead of model
• Not using super() in get_queryset override

3. Given this Django ListView code snippet, what will be the result of accessing the view with URL parameter ?search=apple&order=price?

class ProductListView(ListView):
    model = Product
    def get_queryset(self):
        qs = super().get_queryset()
        search = self.request.GET.get('search')
        order = self.request.GET.get('order')
        if search:
            qs = qs.filter(name__icontains=search)
        if order:
            qs = qs.order_by(order)
        return qs

medium

A. Products filtered to names containing 'apple' and ordered by price

B. All products ordered by price ignoring search

C. Products filtered by price containing 'apple'

D. Error because 'order' parameter is not validated

Solution

1. Step 1: Analyze filtering by 'search' parameter

   The code filters products where name contains 'apple' (case-insensitive).

2. Step 2: Analyze ordering by 'order' parameter

   The code orders the filtered queryset by the 'price' field.

3. Final Answer:

   Products filtered to names containing 'apple' and ordered by price -> Option A

4. Quick Check:

   Filter by search + order by price = Products filtered to names containing 'apple' and ordered by price [OK]

Hint: Filter first, then order queryset in get_queryset [OK]

Common Mistakes:

• Ignoring the search filter when order is present
• Confusing filter field with order field
• Assuming error without validation in this context

4. Identify the error in this Django ListView code that tries to add search and ordering:

class ItemListView(ListView):
    model = Item
    def get_queryset(self):
        qs = super().get_queryset()
        search = self.request.GET.get('search')
        if search:
            qs = qs.filter(name__icontains=search)
        order = self.request.GET.get('order')
        qs = qs.order_by(order)
        return qs

medium

A. Missing pagination in the view

B. Using filter with icontains instead of contains

C. Calling order_by without checking if 'order' is None

D. Not calling super() in get_queryset

Solution

1. Step 1: Check usage of order_by with 'order' parameter

   The code calls order_by(order) without verifying if order is None, causing error if no 'order' param.

2. Step 2: Verify other parts for correctness

   Filter with icontains is valid, super() is called, pagination is optional and not an error here.

3. Final Answer:

   Calling order_by without checking if 'order' is None -> Option C

4. Quick Check:

   order_by needs valid field or check [OK]

Hint: Check if order param exists before calling order_by [OK]

Common Mistakes:

• Assuming filter icontains is wrong
• Forgetting to call super() (not the case here)
• Confusing pagination with query errors

5. You want to implement a Django ListView that allows users to search products by name and order results by price or rating. You also want to prevent invalid ordering fields from causing errors. Which is the best way to implement get_queryset?

hard

A. Filter by search term, then order only if order param is in allowed list ['price', 'rating']

B. Filter by search term, order by any order param without validation

C. Order first by order param, then filter by search term

D. Ignore search and order, just return all products

Solution

1. Step 1: Understand the need for validation of ordering fields

   Allowing only specific fields prevents errors and security issues.

2. Step 2: Apply filtering before ordering and validate order param

   Filter products by search term, then order only if order param is in ['price', 'rating'].

3. Final Answer:

   Filter by search term, then order only if order param is in allowed list ['price', 'rating'] -> Option A

4. Quick Check:

   Validate order param before ordering = Filter by search term, then order only if order param is in allowed list ['price', 'rating'] [OK]

Hint: Validate order fields before ordering queryset [OK]

Common Mistakes:

• Ordering without checking allowed fields
• Ordering before filtering
• Ignoring search parameter completely