Query arguments in GraphQL - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

What is the output of this GraphQL query with arguments?

Given the schema with a books query that accepts an argument author to filter books by author name, what will be the result of this query?

GraphQL

query {
  books(author: "Alice") {
    title
    author
  }
}

A [{"title": "GraphQL Basics", "author": "Bob"}]

B [{"title": "GraphQL Basics", "author": "Alice"}, {"title": "Advanced GraphQL", "author": "Alice"}]

C []

D Error: Unknown argument 'author'

💡 Hint

Think about how the argument filters the list of books by author.

The query filters books where the author is 'Alice', so only books by Alice are returned.

📝 Syntax

intermediate

Which query syntax correctly uses arguments in GraphQL?

Select the query that correctly passes an argument to the user field to fetch a user by ID.

A query { user(id = 5) { name email } }

B query { user { id: 5, name, email } }

C query { user(id: 5) { name email } }

D query { user(id => 5) { name email } }

💡 Hint

Arguments in GraphQL use parentheses and colon syntax.

Option C uses correct syntax: parentheses around arguments and colon to assign values.

❓ optimization

advanced

How to optimize a GraphQL query with multiple arguments to reduce data transfer?

You want to fetch a list of products filtered by category and price range. Which query best reduces unnecessary data transfer?

A query { products(category: "Books", minPrice: 10, maxPrice: 50) { id name price } }

B query { products { id name price category } }

C query { products(category: "Books") { id name price } }

D query { products(minPrice: 10, maxPrice: 50) { id name price } }

💡 Hint

Filtering on the server reduces the amount of data sent.

Option A filters by category and price range, so only matching products are returned, minimizing data.

🔧 Debug

advanced

Why does this GraphQL query with arguments fail?

Given the query below, why does it produce an error?

GraphQL

query {
  user(id: "abc") {
    name
    email
  }
}

A The argument 'id' expects an integer, but a string was provided.

B The query is missing required fields inside 'user'.

C The field 'user' does not accept any arguments.

D The argument 'id' must be passed as a variable, not inline.

💡 Hint

Check the expected type of the argument 'id' in the schema.

If 'id' is defined as an integer, passing a string causes a type error.

🧠 Conceptual

expert

What is the purpose of default argument values in GraphQL queries?

Why would you define default values for arguments in a GraphQL schema?

A To restrict access to certain fields based on argument values.

B To force clients to always provide argument values.

C To improve query execution speed by caching results.

D To allow queries to omit arguments and still get predictable results.

💡 Hint

Think about what happens when a client does not provide an argument.

Default argument values let the server use a fallback value when the client omits the argument, ensuring consistent behavior.

Practice

1. What is the purpose of query arguments in GraphQL?

easy

A. To write comments inside queries

B. To define new types in the schema

C. To specify exactly what data you want from the server

D. To create mutations for updating data

Solution

1. Step 1: Understand what query arguments do

   Query arguments allow you to tell the server exactly which data you want, like filtering or limiting results.

2. Step 2: Compare options to the purpose

   Only To specify exactly what data you want from the server describes specifying data in queries. Other options describe unrelated tasks.

3. Final Answer:

   To specify exactly what data you want from the server -> Option C

4. Quick Check:

   Query arguments = specify data [OK]

Hint: Arguments filter or limit data inside parentheses [OK]

Common Mistakes:

• Confusing arguments with schema definitions
• Thinking arguments create mutations
• Using arguments for comments

2. Which of the following is the correct syntax to pass an argument named id with value 5 to a GraphQL query field user?

easy

A. user(id: 5) { name }

B. user[id=5] { name }

C. user{id=5} { name }

D. user(id=5) { name }

Solution

1. Step 1: Recall GraphQL argument syntax

   Arguments go inside parentheses after the field name, with colon separating name and value.

2. Step 2: Check each option's syntax

   user(id: 5) { name } uses parentheses and colon correctly. Options B and C use brackets or braces incorrectly. user(id=5) { name } uses equals sign instead of colon.

3. Final Answer:

   user(id: 5) { name } -> Option A

4. Quick Check:

   Arguments use (name: value) syntax [OK]

Hint: Use parentheses and colon for arguments (name: value) [OK]

Common Mistakes:

• Using square brackets instead of parentheses
• Using equals sign instead of colon
• Placing arguments inside braces

3. Given the query { books(limit: 2) { title } } and a database with books titled 'A', 'B', 'C', what will the query return?

medium

A. [{ title: 'A' }, { title: 'B' }, { title: 'C' }]

B. [] (empty list)

C. Error: 'limit' is not a valid argument

D. [{ title: 'A' }, { title: 'B' }]

Solution

1. Step 1: Understand the limit argument

   The limit: 2 argument restricts the number of returned books to 2.

2. Step 2: Predict the returned data

   From books 'A', 'B', 'C', only the first two 'A' and 'B' will be returned.

3. Final Answer:

   [{ title: 'A' }, { title: 'B' }] -> Option D

4. Quick Check:

   limit: 2 returns 2 items [OK]

Hint: Limit argument restricts number of results [OK]

Common Mistakes:

• Assuming all items return ignoring limit
• Thinking limit causes error
• Expecting empty list when data exists

4. Identify the error in this GraphQL query: { users(age: 'twenty') { name } } assuming age expects an integer argument.

medium

A. The field name 'users' is invalid

B. The argument value should be an integer, not a string

C. Missing curly braces around the argument

D. The query is correct and will run without errors

Solution

1. Step 1: Check argument type requirements

   The age argument expects an integer, but the query passes a string 'twenty'.

2. Step 2: Identify the type mismatch error

   Passing a string instead of an integer causes a type error in GraphQL.

3. Final Answer:

   The argument value should be an integer, not a string -> Option B

4. Quick Check:

   Argument types must match schema [OK]

Hint: Match argument types exactly as defined [OK]

Common Mistakes:

• Passing strings instead of numbers
• Assuming field names cause errors
• Thinking braces are needed around arguments

5. You want to query a list of products sorted by price descending and limited to 3 items. Which query correctly uses arguments to achieve this?

hard

A. { products(sortBy: "price_desc", limit: 3) { name price } }

B. { products(limit: 3, order: "desc") { name price } }

C. { products(sort: price, limit: 3) { name price } }

D. { products(limit: 3, sortBy: "desc_price") { name price } }

Solution

1. Step 1: Identify correct argument names and values

   The argument sortBy with value "price_desc" clearly indicates sorting by price descending. The limit argument limits results to 3.

2. Step 2: Evaluate each option's correctness

   { products(sortBy: "price_desc", limit: 3) { name price } } uses both arguments correctly. { products(limit: 3, order: "desc") { name price } } uses 'order' which may be invalid. { products(sort: price, limit: 3) { name price } } uses 'sort' without quotes and no direction. { products(limit: 3, sortBy: "desc_price") { name price } } uses 'desc_price' which is not standard.

3. Final Answer:

   { products(sortBy: "price_desc", limit: 3) { name price } } -> Option A

4. Quick Check:

   Use correct argument names and values [OK]

Hint: Use exact argument names and values from schema [OK]

Common Mistakes:

• Using wrong argument names like 'order' or 'sort'
• Passing unquoted values for strings
• Mixing argument order incorrectly