In this lesson, we will define basic types and write simple queries in GraphQL using Apollo Server. By the end, you'll create a basic GraphQL server to fetch a list of books, building on what you've learned about setting up a GraphQL server.

We'll start by setting up a new Apollo Server instance to manage our GraphQL server using Apollo Server 4. Let's proceed step-by-step.

1. Define the GraphQL schema:

   In this schema:

   • The Book type has title and author fields, both of which are strings.
   • The Query type includes a books field that returns an array of Book objects.

2. Create sample data:

   This array will act as our in-memory database of books.

3. Define resolvers:

   Here, the resolver for the books query simply returns the books array we defined earlier.

4. Initialize, configure, and start Apollo Server:

   Running this command will start the server and print the URL where it's accessible.

With the server running, let's write and execute a query to fetch the list of books.

When a query is sent to the GraphQL server:

• The server parses the query to ensure it matches the schema.
• The server validates the query to check for any syntax errors or mismatched fields.
• The server executes the resolver associated with the query field (books).
• The data returned by the resolver is formatted into a JSON response and sent back to the client.

This script:

• Sends a POST request to the server with a query to fetch books.
• Logs the response, which should include the list of books with their titles and authors.

The script outputs:

This output confirms that our server correctly handles the query and returns the expected data.

In this lesson, we:

• Created a schema with a basic type (Book).
• Set up resolvers to fetch data.
• Wrote and ran queries to retrieve a list of books.

Next, you will practice what you've learned by tackling exercises that help solidify these concepts. The following lessons will cover more complex queries and mutations.

Happy coding!