SQL database resolvers in GraphQL - Mini Project: Build & Apply

Build SQL Database Resolvers for GraphQL

📖 Scenario: You are building a simple GraphQL API for a bookstore. The data is stored in a SQL database. You want to create resolvers that fetch data from the SQL database when a client queries the GraphQL API.

🎯 Goal: Create SQL database resolvers in GraphQL that fetch book data from a SQL database table called books. You will set up the initial data structure, add configuration for the database connection, write the core resolver logic, and complete the resolver setup.

📋 What You'll Learn

Create a GraphQL resolver function named getBooks that queries the books table

Add a configuration variable dbClient to connect to the SQL database

Write the SQL query inside the resolver to select all columns from books

Complete the resolver export so it can be used in the GraphQL server

💡 Why This Matters

🌍 Real World

GraphQL APIs often need to fetch data from SQL databases. Writing resolvers that query SQL tables is a common task in backend development.

💼 Career

Backend developers and full-stack engineers frequently write database resolvers to connect GraphQL APIs with SQL databases, enabling efficient data retrieval and manipulation.

1

DATA SETUP: Create the resolver function skeleton

Create a function called getBooks that takes parent, args, and context as parameters. The function should be asynchronous and return an empty array for now.

GraphQL

async function getBooks(parent, args, context) {
  // Your code here
}

Hint

Define an async function named getBooks with the parameters parent, args, and context. Return an empty array inside.

2

CONFIGURATION: Add the database client variable

Add a constant variable called dbClient that represents the SQL database client connection. For this example, set it to { query: async () => ({ rows: [] }) } to simulate a database client.

GraphQL

const dbClient = { query: async () => ({ rows: [] }) };

async function getBooks(parent, args, context) {
  return [];
  // Your code here
}

Hint

Create a constant dbClient that has a query method returning an object with an empty rows array.

3

CORE LOGIC: Write the SQL query inside the resolver

Inside the getBooks function, use dbClient.query to run the SQL query SELECT * FROM books;. Await the result and return the rows property from the query result.

GraphQL

const dbClient = { query: async () => ({ rows: [] }) };

async function getBooks(parent, args, context) {
  // Your code here
}

Hint

Use await dbClient.query('SELECT * FROM books;') and return the rows from the result.

4

COMPLETION: Export the resolver function

Add an export statement that exports an object with a Query property. Inside Query, assign the getBooks function to the books field.

GraphQL

const dbClient = { query: async () => ({ rows: [] }) };

async function getBooks(parent, args, context) {
  const result = await dbClient.query('SELECT * FROM books;');
  return result.rows;
}

// Your code here

Hint

Export an object named resolvers with a Query property that maps books to getBooks.