Migration from REST to GraphQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a simple GraphQL query to fetch user names.

GraphQL

query { users { [1] } }

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

Aemail

Bname

Cid

Dpassword

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing 'email' instead of 'name' when the task asks for user names.

Selecting 'password' which is sensitive and usually not fetched.

The name field fetches user names in GraphQL queries.

2fill in blank

medium

Complete the code to fetch a user's posts with their titles.

GraphQL

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

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

Atitle

Bauthor

Cdate

Dcontent

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing 'content' which fetches the body, not the title.

Selecting 'author' which is not a post title.

The title field fetches the post titles in GraphQL.

3fill in blank

hard

Fix the error in the GraphQL mutation to create a new user with a name.

GraphQL

mutation { createUser(input: { [1]: "Alice" }) { id name } }

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

Ausername

Bpassword

Cemail

Dname

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'username' which may not be defined in the schema.

Using 'email' or 'password' which are different fields.

The input field should be name to match the schema for creating a user.

4fill in blank

hard

Fill both blanks to query users with their names and posts' titles.

GraphQL

query { users { [1] posts { [2] } } }

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

Aname

Btitle

Cdate

Demail

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'email' instead of 'name' for users.

Choosing 'date' instead of 'title' for posts.

The first blank should be name to get user names, and the second blank title to get post titles.

5fill in blank

hard

Fill all three blanks to write a mutation that updates a post's title and content by id.

GraphQL

mutation { updatePost(id: "[1]", input: { [2]: "New Title", [3]: "Updated content" }) { id title content } }

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

A1

Btitle

Ccontent

DpostId

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'postId' instead of just the id value.

Swapping 'title' and 'content' fields.

The post id is 1, and the input fields to update are title and content.

Practice

1. What is a key advantage of migrating from REST to GraphQL for database queries?

easy

A. REST automatically optimizes data fetching without changes.

B. You can request exactly the data you need in a single query.

C. GraphQL requires multiple requests to get all data.

D. GraphQL does not support querying nested data.

Solution

1. Step 1: Understand REST vs GraphQL data fetching

   REST often requires multiple requests or returns extra data, while GraphQL lets you specify exactly what you want.

2. Step 2: Identify the main benefit of GraphQL

   GraphQL reduces over-fetching and under-fetching by allowing precise queries in one request.

3. Final Answer:

   You can request exactly the data you need in a single query. -> Option B

4. Quick Check:

   GraphQL precise data fetching = C [OK]

Hint: GraphQL = one request, exact data [OK]

Common Mistakes:

• Thinking GraphQL needs multiple requests
• Believing REST auto-optimizes data fetching
• Assuming GraphQL can't query nested data

2. Which of the following is the correct way to define a simple GraphQL query to get a user's name and email?

easy

A. { user: { name, email } }

B. GET /user { name, email }

C. query { user { name, email } }

D. SELECT name, email FROM user

Solution

1. Step 1: Recognize GraphQL query syntax

   GraphQL queries start with the keyword 'query' followed by the fields requested inside braces.

2. Step 2: Compare options to GraphQL syntax

   query { user { name, email } } matches the correct GraphQL query format; others are REST, SQL, or invalid syntax.

3. Final Answer:

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

4. Quick Check:

   GraphQL query syntax = D [OK]

Hint: GraphQL queries start with 'query' keyword [OK]

Common Mistakes:

• Using REST or SQL syntax instead of GraphQL
• Omitting the 'query' keyword
• Incorrect braces placement

3. Given this GraphQL query:
query { book(id: "1") { title author { name } } }
What is the expected shape of the returned data?

medium

A. {"data": {"book": {"title": "Book Title", "author": {"name": "Author Name"}}}}

B. {"book": {"title": "Book Title", "author": "Author Name"}}

C. {"data": {"book": {"title": "Book Title", "author": "Author Name"}}}

D. {"data": {"book": ["title", "author"]}}

Solution

1. Step 1: Understand GraphQL nested response format

   GraphQL returns data inside a 'data' object, preserving nested structure matching the query.

2. Step 2: Match query fields to response structure

   The query requests 'title' and nested 'author' with 'name', so response nests 'author' as an object with 'name'.

3. Final Answer:

   {"data": {"book": {"title": "Book Title", "author": {"name": "Author Name"}}}} -> Option A

4. Quick Check:

   Nested data in 'data' key = A [OK]

Hint: GraphQL response nests data under 'data' key [OK]

Common Mistakes:

• Returning author as string instead of object
• Missing 'data' wrapper in response
• Using arrays instead of objects for fields

4. You migrated a REST endpoint to GraphQL but get an error: Cannot query field 'userName' on type 'User'. What is the likely cause?

medium

A. GraphQL does not support querying user names.

B. The REST endpoint is down.

C. The query syntax is missing curly braces.

D. The GraphQL schema does not define a 'userName' field on 'User' type.

Solution

1. Step 1: Analyze the error message

   The error says 'userName' is not a valid field on 'User' type, indicating schema mismatch.

2. Step 2: Understand GraphQL schema role

   GraphQL queries must match fields defined in the schema; missing fields cause errors.

3. Final Answer:

   The GraphQL schema does not define a 'userName' field on 'User' type. -> Option D

4. Quick Check:

   Schema field missing = A [OK]

Hint: Check schema fields match query fields [OK]

Common Mistakes:

• Blaming REST endpoint for GraphQL schema errors
• Ignoring schema definitions
• Assuming GraphQL can't query user names

5. During migration from REST to GraphQL, you want to avoid over-fetching user data. Which approach best achieves this?

hard

A. Define a GraphQL query that requests only the needed user fields like name and email.

B. Keep using the REST endpoint but add query parameters to limit fields.

C. Fetch all user data and filter unwanted fields on the client side.

D. Use multiple GraphQL queries to get each user field separately.

Solution

1. Step 1: Understand over-fetching in REST vs GraphQL

   REST often returns full objects; GraphQL lets you specify exactly which fields to fetch.

2. Step 2: Choose the best method to limit data fetched

   Defining a GraphQL query with only needed fields avoids over-fetching efficiently in one request.

3. Final Answer:

   Define a GraphQL query that requests only the needed user fields like name and email. -> Option A

4. Quick Check:

   Selective field query = B [OK]

Hint: Request only needed fields in GraphQL query [OK]

Common Mistakes:

• Fetching all data then filtering client-side
• Using multiple queries instead of one precise query
• Relying on REST query parameters only