Why GraphQL exists - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a GraphQL query that fetches a user's name.

GraphQL

query { user(id: "1") { [1] } }

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

Apassword

Bage

Cemail

Dname

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing fields that are not related to the user's name.

The name field is requested to get the user's name in the query.

2fill in blank

medium

Complete the code to request only the needed fields in a GraphQL query.

GraphQL

query { product(id: "5") { id [1] } }

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

Aprice

Bdescription

Cstock

Dall

Attempts:

3 left

💡 Hint

Common Mistakes

Requesting all fields at once, which GraphQL does not support with 'all'.

GraphQL lets you request only the fields you need, like price here.

3fill in blank

hard

Fix the error in the GraphQL query to fetch a user's email.

GraphQL

query { user(id: "2") { [1] } }

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

Aemail

Bemails

Cmail

DuserEmail

Attempts:

3 left

💡 Hint

Common Mistakes

Using plural or incorrect field names like 'emails' or 'mail'.

The correct field name to get the user's email is email.

4fill in blank

hard

Fill both blanks to complete a GraphQL mutation that updates a user's name.

GraphQL

mutation { updateUser(id: "3", input: { name: [1] }) { [2] } }

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

A"Alice"

Bname

Cid

D"Bob"

Attempts:

3 left

💡 Hint

Common Mistakes

Not quoting the new name or requesting wrong fields in the response.

The mutation sets the user's name to "Alice" and requests the updated name field in the response.

5fill in blank

hard

Fill all three blanks to complete a GraphQL query fetching a post's title and author's name.

GraphQL

query { post(id: [1]) { [2] author { [3] } } }

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

A"10"

Btitle

Cname

Dcontent

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong id format or requesting wrong fields like 'content' instead of 'title'.

The query fetches the post with id "10", requests its title, and the name of the author.

Practice

1. Why was GraphQL created as a new way to request data from APIs?

easy

A. To force clients to download all data every time.

B. To make APIs slower and more complex.

C. To let clients ask for exactly the data they need, no more, no less.

D. To replace databases with a new storage system.

Solution

1. Step 1: Understand the problem GraphQL solves

   Traditional APIs often send too much or too little data, causing inefficiency.

2. Step 2: Identify GraphQL's main benefit

   GraphQL allows clients to specify exactly what data they want, improving efficiency.

3. Final Answer:

   To let clients ask for exactly the data they need, no more, no less. -> Option C

4. Quick Check:

   GraphQL = precise data requests [OK]

Hint: GraphQL lets you ask only for what you need [OK]

Common Mistakes:

• Thinking GraphQL makes APIs slower
• Believing GraphQL replaces databases
• Assuming GraphQL sends all data always

2. Which of the following is the correct way to request a user's name and email in GraphQL?

easy

A. query { user name email }

B. query { user { name, email } }

C. query user { name, email }

D. query { user: name, email }

Solution

1. Step 1: Recall GraphQL query syntax

   GraphQL queries use curly braces to specify fields inside objects.

2. Step 2: Check each option's syntax

   query { user { name, email } } correctly nests fields inside user with commas separating fields.

3. Final Answer:

   query { user { name, email } } -> Option B

4. Quick Check:

   Correct GraphQL query syntax = query { user { name, email } } [OK]

Hint: Fields inside braces, separated by commas [OK]

Common Mistakes:

• Missing braces around nested fields
• Using colons incorrectly in queries
• Omitting commas between fields

3. Given this GraphQL query:
query { book(id: "1") { title author { name } } }
What data will the client receive?

medium

A. { "book": { "title": "1984", "author": { "name": "George Orwell" } } }

B. { "book": { "title": "1984" } }

C. { "title": "1984", "author": "George Orwell" }

D. { "book": { "name": "George Orwell" } }

Solution

1. Step 1: Analyze the query fields

   The query asks for book with id "1", requesting title and nested author name.

2. Step 2: Match query fields to response structure

   The response includes book object with title and author object containing name.

3. Final Answer:

   { "book": { "title": "1984", "author": { "name": "George Orwell" } } } -> Option A

4. Quick Check:

   Nested fields return nested objects [OK]

Hint: Nested fields return nested objects in response [OK]

Common Mistakes:

• Expecting flat objects for nested fields
• Missing nested author object
• Ignoring requested fields in response

4. This GraphQL query has an error:
query { user { name, email } }
Which is the most likely cause?

medium

A. The query is missing a closing brace.

B. GraphQL queries cannot have commas between fields.

C. Fields 'name' and 'email' cannot be requested together.

D. The server schema does not have a 'user' field.

Solution

1. Step 1: Check query syntax

   The query syntax is correct with braces and commas properly placed.

2. Step 2: Consider schema compatibility

   If the server schema lacks 'user' field, the query will fail despite correct syntax.

3. Final Answer:

   The server schema does not have a 'user' field. -> Option D

4. Quick Check:

   Schema mismatch causes query errors [OK]

Hint: Check if fields exist in server schema [OK]

Common Mistakes:

• Assuming syntax error when schema is missing fields
• Thinking commas are not allowed between fields
• Believing fields cannot be requested together

5. A client wants to fetch a list of products with only their names and prices to improve app speed. Which GraphQL feature helps achieve this?

hard

A. Requesting only specific fields in the query to reduce data transfer.

B. Using mutations to update product data.

C. Fetching all product details and filtering on the client side.

D. Using subscriptions to get real-time updates.

Solution

1. Step 1: Understand the client's goal

   The client wants to improve speed by reducing unnecessary data.

2. Step 2: Identify GraphQL feature that fits

   GraphQL allows requesting only needed fields, minimizing data sent over network.

3. Final Answer:

   Requesting only specific fields in the query to reduce data transfer. -> Option A

4. Quick Check:

   Selective field requests improve performance [OK]

Hint: Ask only for needed fields to speed up apps [OK]

Common Mistakes:

• Confusing queries with mutations
• Fetching all data then filtering client-side
• Using subscriptions when not needed