First GraphQL query - Mini Project: Build & Apply

First GraphQL query

📖 Scenario: You are building a simple app to show information about books in a library. The library database has books with titles and authors.

🎯 Goal: Write a GraphQL query to get the title and author of all books from the library database.

📋 What You'll Learn

Create a GraphQL query named GetBooks

Query the books field

Request the title and author fields for each book

💡 Why This Matters

🌍 Real World

GraphQL queries are used to fetch exactly the data you want from APIs, making apps faster and more efficient.

💼 Career

Knowing how to write GraphQL queries is important for frontend and backend developers working with modern APIs.

1

Create the query structure

Write the start of a GraphQL query named GetBooks that queries the books field.

GraphQL

# Your code here
query GetBooks {
  books {

  }
}

Hint

Start with query GetBooks { and inside it add books { }.

2

Add the title field

Inside the books field, add the title field to request the book titles.

GraphQL

query GetBooks {
  books {
    # Add the title field here
  }
}

Hint

Inside books { }, add a line with title.

3

Add the author field

Add the author field inside the books field to request the author names.

GraphQL

query GetBooks {
  books {
    title
    # Add the author field here
  }
}

Hint

Inside books { }, add a line with author below title.

4

Complete the query

Make sure the query is complete with matching braces and no extra fields.

GraphQL

query GetBooks {
  books {
    title
    author
  }
}
# Query complete

Hint

Check that all braces match and only title and author are requested inside books.

Practice

1. What does a basic GraphQL query do?

easy

A. It asks for specific data by listing fields inside curly braces.

B. It updates data in the database.

C. It deletes data from the server.

D. It creates a new database schema.

Solution

1. Step 1: Understand GraphQL query purpose

   A GraphQL query is designed to request specific data from a server.

2. Step 2: Identify query syntax

   The query lists the fields wanted inside curly braces to specify what data to fetch.

3. Final Answer:

   It asks for specific data by listing fields inside curly braces. -> Option A

4. Quick Check:

   GraphQL query = request data [OK]

Hint: Remember: queries fetch data by listing fields [OK]

Common Mistakes:

• Confusing queries with mutations
• Thinking queries modify data
• Mixing query syntax with SQL

2. Which of the following is the correct syntax for a simple GraphQL query to get a user's name?

easy

A. query { user { name } }

B. query user { name }

C. { user name }

D. query user name { }

Solution

1. Step 1: Review GraphQL query structure

   A query starts with the keyword 'query' (optional), followed by curly braces enclosing the fields.

2. Step 2: Check each option's syntax

   query { user { name } } correctly uses 'query' and nested braces for user and name fields.

3. Final Answer:

   query { user { name } } -> Option A

4. Quick Check:

   Correct braces and field nesting = query { user { name } } [OK]

Hint: Use nested braces for nested fields [OK]

Common Mistakes:

• Missing curly braces
• Incorrect field nesting
• Wrong keyword placement

3. Given this GraphQL query:

query { book { title author } }

What data will the server return?

medium

A. SyntaxError: Missing fields

B. { "data": { "book": "title author" } }

C. { "book": { "title": "string", "author": "string" } }

D. { "data": { "book": { "title": "string", "author": "string" } } }

Solution

1. Step 1: Understand GraphQL response format

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

2. Step 2: Match query fields to response

   The query asks for 'book' with 'title' and 'author', so response includes these nested fields.

3. Final Answer:

   { "data": { "book": { "title": "string", "author": "string" } } } -> Option D

4. Quick Check:

   Response matches query structure [OK]

Hint: Response wraps requested fields inside 'data' object [OK]

Common Mistakes:

• Omitting 'data' wrapper in response
• Returning fields as a string
• Confusing syntax error with valid query

4. Identify the error in this GraphQL query:

query { user { id name 

medium

A. Fields 'id' and 'name' are invalid.

B. Incorrect keyword 'query' used.

C. Missing closing curly braces for 'user' and 'query'.

D. Query should not have nested fields.

Solution

1. Step 1: Check query syntax completeness

   The query opens braces for 'user' and 'query' but does not close them.

2. Step 2: Confirm correct use of keywords and fields

   'query' keyword is correct; 'id' and 'name' are valid fields; nested fields are allowed.

3. Final Answer:

   Missing closing curly braces for 'user' and 'query'. -> Option C

4. Quick Check:

   Unclosed braces cause syntax error [OK]

Hint: Count opening and closing braces carefully [OK]

Common Mistakes:

• Forgetting to close all braces
• Assuming keywords are wrong
• Thinking nested fields are invalid

5. You want to fetch a list of users with their id and name using GraphQL. Which query correctly does this assuming the server has a 'users' field returning a list?

hard

A. query { users: id, name }

B. query { users { id name } }

C. query { user { id name } }

D. query users { id name }

Solution

1. Step 1: Identify the correct root field for multiple users

   The server field for multiple users is 'users', not 'user'.

2. Step 2: Check query syntax for nested fields

   query { users { id name } } correctly queries 'users' with nested 'id' and 'name' fields inside braces.

3. Final Answer:

   query { users { id name } } -> Option B

4. Quick Check:

   Correct root field and nested fields = query { users { id name } } [OK]

Hint: Use plural field for lists, nest fields inside braces [OK]

Common Mistakes:

• Using singular 'user' for list data
• Incorrect field alias syntax
• Omitting braces for nested fields