Query arguments in GraphQL - Mini Project: Build & Apply

GraphQL Query Arguments

📖 Scenario: You are building a simple GraphQL API for a bookstore. You want to allow users to query for books by specifying arguments like id or author.

🎯 Goal: Create a GraphQL query that uses arguments to fetch specific books by id and by author.

📋 What You'll Learn

Define a Book type with fields id, title, and author.

Create a Query type with a bookById field that takes an id argument of type ID! and returns a Book.

Create a Query type with a booksByAuthor field that takes an author argument of type String! and returns a list of Book.

Write example queries using arguments to fetch a book by id and books by author.

💡 Why This Matters

🌍 Real World

GraphQL APIs often require arguments to fetch specific data, like searching for a book by its ID or author.

💼 Career

Understanding query arguments is essential for backend developers and API designers working with GraphQL to build flexible and efficient data queries.

1

Define the Book type

Create a GraphQL type called Book with fields id of type ID!, title of type String!, and author of type String!.

GraphQL

# Define the Book type with id, title, and author fields

Need a hint?

Use the type keyword to define a new type. Each field needs a name and a type with an exclamation mark for required fields.

2

Add Query fields with arguments

Add a Query type with two fields: bookById that takes an id argument of type ID! and returns a Book, and booksByAuthor that takes an author argument of type String! and returns a list of Book.

GraphQL

type Book {
  id: ID!
  title: String!
  author: String!
}

# Add Query type with bookById and booksByAuthor fields with arguments

Need a hint?

Define the Query type with fields that accept arguments inside parentheses. Use square brackets [] to indicate a list return type.

3

Write a query to fetch a book by id

Write a GraphQL query named GetBookById that calls bookById with an argument id set to "1" and requests the id, title, and author fields.

GraphQL

type Book {
  id: ID!
  title: String!
  author: String!
}

type Query {
  bookById(id: ID!): Book
  booksByAuthor(author: String!): [Book]
}

# Write a query named GetBookById to fetch bookById with id "1"

Need a hint?

Use the query keyword followed by the query name. Pass the argument inside parentheses and request the fields inside curly braces.

4

Write a query to fetch books by author

Write a GraphQL query named GetBooksByAuthor that calls booksByAuthor with an argument author set to "Jane Austen" and requests the id, title, and author fields for each book.

GraphQL

type Book {
  id: ID!
  title: String!
  author: String!
}

type Query {
  bookById(id: ID!): Book
  booksByAuthor(author: String!): [Book]
}

query GetBookById {
  bookById(id: "1") {
    id
    title
    author
  }
}

# Write a query named GetBooksByAuthor to fetch booksByAuthor with author "Jane Austen"

Need a hint?

Similar to the previous query, but call booksByAuthor with the author argument and request the fields for each book in the list.