Nested field queries in GraphQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to query the name of all books.

GraphQL

query { books { [1] } }

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

Atitle

Byear

Cauthor

Dpublisher

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing author instead of title.

Using a field that does not exist in the schema.

The title field gives the name of each book.

2fill in blank

medium

Complete the code to get the author's name for each book.

GraphQL

query { books { author { [1] } } }

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

AbirthYear

Bid

Cnationality

Dname

Attempts:

3 left

💡 Hint

Common Mistakes

Selecting id instead of name.

Choosing a field unrelated to the author's name.

The name field inside author gives the author's name.

3fill in blank

hard

Fix the error in the query to get the book's title and the author's birth year.

GraphQL

query { books { title author { [1] } } }

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

Abirth_year

BbirthYear

Cbirthyear

DyearBorn

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect casing like birthyear.

Using snake_case instead of camelCase.

The correct field name is birthYear with camelCase.

4fill in blank

hard

Fill both blanks to query each book's title and the author's nationality.

GraphQL

query { books { [1] author { [2] } } }

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

Atitle

Bname

Cnationality

DbirthYear

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up name and nationality.

Using fields that don't exist in the schema.

The book's title is title and the author's nationality is nationality.

5fill in blank

hard

Fill all three blanks to query the book's title, author's name, and author's birth year.

GraphQL

query { books { [1] author { [2] [3] } } }

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

Atitle

Bname

CbirthYear

Dnationality

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to include all three fields.

Using incorrect field names or casing.

The book's title is title, the author's name is name, and the birth year is birthYear.

Practice

1. What is the main purpose of using nested field queries in GraphQL?

easy

A. To fetch related data in a single request

B. To update multiple records at once

C. To delete nested data automatically

D. To create new nested fields in the schema

Solution

1. Step 1: Understand nested queries

   Nested queries allow fetching related data together, reducing multiple requests.

2. Step 2: Compare options

   Only To fetch related data in a single request describes fetching related data in one request, which is the key benefit.

3. Final Answer:

   To fetch related data in a single request -> Option A

4. Quick Check:

   Nested queries = fetch related data [OK]

Hint: Nested queries fetch related data together in one request [OK]

Common Mistakes:

• Thinking nested queries update or delete data
• Confusing nested queries with schema creation
• Assuming nested queries only fetch top-level fields

2. Which of the following is the correct syntax to query a nested field author inside book in GraphQL?

easy

A. { book > author { name } }

B. { book { author { name } } }

C. { book: { author { name } } }

D. { book.author { name } }

Solution

1. Step 1: Recall GraphQL nested syntax

   Nested fields are queried using curly braces inside parent fields without dots or colons.

2. Step 2: Check each option

   { book { author { name } } } uses correct nested braces. Options A, B, and C use invalid syntax like dots, colons, or arrows.

3. Final Answer:

   { book { author { name } } } -> Option B

4. Quick Check:

   Nested fields use braces, not dots or colons [OK]

Hint: Use curly braces for nested fields, no dots or colons [OK]

Common Mistakes:

• Using dot notation instead of braces
• Adding colons inside query fields
• Using arrows or other symbols for nesting

3. Given this GraphQL query:

{ user(id: 1) { name posts { title comments { text } } } }

What fields will be included in the response?

medium

A. User's name and comments' texts only

B. Only user's name and posts' titles

C. User's name, posts' titles, and comments' texts

D. Only posts' titles and comments' texts

Solution

1. Step 1: Analyze the query structure

   The query requests user with id 1, then nested fields: name, posts with title, and comments with text inside posts.

2. Step 2: Determine included fields

   All requested fields appear in the response: user's name, posts' titles, and comments' texts.

3. Final Answer:

   User's name, posts' titles, and comments' texts -> Option C

4. Quick Check:

   Nested query fields = all requested fields [OK]

Hint: Response includes all nested fields requested in braces [OK]

Common Mistakes:

• Ignoring nested comments field
• Assuming only top-level fields return
• Confusing which fields are nested

4. Identify the error in this GraphQL query:

{ product { id name { first last } } }

medium

A. Missing parentheses after product

B. Field id cannot be queried with name

C. Curly braces are not allowed inside queries

D. Field name is treated as an object but should be scalar

Solution

1. Step 1: Understand field types

   If name is a scalar (like string), it cannot have nested fields first and last.

2. Step 2: Check query structure

   The query treats name as an object with nested fields, causing an error if schema defines it as scalar.

3. Final Answer:

   Field name is treated as an object but should be scalar -> Option D

4. Quick Check:

   Scalar fields cannot have nested fields [OK]

Hint: Only object fields can have nested fields; scalars cannot [OK]

Common Mistakes:

• Assuming all fields can have nested fields
• Adding parentheses unnecessarily
• Misunderstanding query braces usage

5. You want to fetch a list of authors with their books and each book's reviews including rating and comment. Which query correctly nests these fields?

hard

A. { authors { name books { title reviews { rating comment } } } }

B. { authors { name books { title } reviews { rating comment } } }

C. { authors { name { books { title reviews { rating comment } } } } }

D. { authors { name books reviews { rating comment } } }

Solution

1. Step 1: Understand nesting requirements

   Reviews belong to each book, so reviews must be nested inside books.

2. Step 2: Check each option's nesting

   { authors { name books { title reviews { rating comment } } } } correctly nests reviews inside books. { authors { name books { title } reviews { rating comment } } } places reviews outside books. { authors { name { books { title reviews { rating comment } } } } } nests books inside name incorrectly. { authors { name books reviews { rating comment } } } misses nesting reviews inside books.

3. Final Answer:

   { authors { name books { title reviews { rating comment } } } } -> Option A

4. Quick Check:

   Nested fields must follow data hierarchy [OK]

Hint: Nest fields inside their parent objects to match data structure [OK]

Common Mistakes:

• Placing nested fields at wrong levels
• Nesting fields inside scalar fields
• Missing braces for nested objects