Entity references in GraphQL - Mini Project: Build & Apply

Building Entity References in GraphQL

📖 Scenario: You are creating a simple GraphQL API for a library system. The system has books and authors. Each book references an author by ID.

🎯 Goal: Build a GraphQL schema that defines Author and Book types, where each Book references an Author by ID. Then create a query to fetch books with their author details.

📋 What You'll Learn

Define an Author type with fields id and name

Define a Book type with fields id, title, and authorId

Add a query books that returns a list of Book

Add a field author on Book that resolves the author details by authorId

💡 Why This Matters

🌍 Real World

GraphQL schemas with entity references are used in APIs to model relationships between data, like books and authors in a library system.

💼 Career

Understanding entity references in GraphQL is essential for backend developers building APIs that serve connected data efficiently.

1

Define Author and Book types

Create GraphQL types Author with fields id: ID! and name: String!, and Book with fields id: ID!, title: String!, and authorId: ID!.

GraphQL

# Define Author and Book types
# Your code here

Need a hint?

Use type keyword to define GraphQL types. Fields must have types with exclamation marks for required fields.

2

Add books query

Add a Query type with a field books that returns a list of Book (use [Book!]! as the return type).

GraphQL

type Author {
  id: ID!
  name: String!
}

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

# Add Query type with books field
# Your code here

Need a hint?

The Query type is the entry point for queries. Use square brackets for lists and exclamation marks for non-null.

3

Add author field to Book type

Add a field author to the Book type that returns an Author (type Author!). This will be used to fetch the author details for each book.

GraphQL

type Author {
  id: ID!
  name: String!
}

type Book {
  id: ID!
  title: String!
  authorId: ID!
  # Add author field here
}

type Query {
  books: [Book!]!
}

Need a hint?

Add the author field with type Author! inside the Book type.

4

Complete schema with entity references

Combine all previous steps to form the complete GraphQL schema with Author, Book types, the author field on Book, and the books query.

GraphQL

# Review and finalize the complete schema
# Your code here

Need a hint?

Make sure all types and fields from previous steps are included correctly.