ทำความเข้าใจมิวเทชัน GraphQL

Welcome! In GraphQL, you interact with your data in two main ways: fetching it and changing it.

Mutations are the operations you use to modify data on your server. Think of them as the 'write' actions of your API.

Before diving deep into mutations, let's quickly recall Queries.

• Queries are used to fetch data from your server.
• They are designed to be read-only operations.
• Running a query should never change any data on the backend. They are side-effect free.

Now, for making changes, we use Mutations.

Mutations are specifically designed for:

• Creating new data (e.g., adding a new user).
• Updating existing data (e.g., changing a user's email).
• Deleting data (e.g., removing a post).

They are the equivalent of POST, PUT, DELETE requests in REST APIs.

The core difference between queries and mutations lies in their side effects.

• Queries: Have NO side effects. They just retrieve data.
• Mutations: Are INTENDED to have side effects. They change data on the server.

This clear separation helps you understand how an operation will impact your backend.

A GraphQL mutation request looks similar to a query, but it starts with the mutation keyword.

Here's a basic structure:

The OperationName is optional but good for debugging.

Let's imagine we're creating a new user. In a real application, a mutation would send this data to the server. For now, let's simulate the action of 'creating' something in Java.

This simple program shows how a 'create' operation might conceptually work, returning a success message.

To create or update data, mutations need input. This input is passed using arguments, just like with queries.

Often, you'll see an input type used to group multiple arguments into a single, organized object, making your schema cleaner.

• Example: createUser(input: CreateUserInput)

After a mutation executes, it returns a result. What it returns is up to you when designing your schema.

Common return types include:

• The modified object (e.g., the newly created user).
• A status object indicating success/failure.
• A list of affected IDs.

This allows clients to immediately update their UI with the new data.

Any time you need to change data on your backend, you'll reach for a mutation. Here are some common use cases:

• Registering a new user account.
• Adding an item to a shopping cart.
• Updating a user's profile information.
• Posting a new comment or article.
• Deleting a record from a database.

You've learned the fundamental difference between GraphQL queries and mutations. Let's test your understanding!

Great job! You now understand the core concept of GraphQL Mutations.

• Mutations are GraphQL operations for modifying data.
• They are distinct from Queries, which are read-only.
• Mutations are designed to have side effects on your server's data.
• They are used for creating, updating, and deleting records.

Next, we'll dive into implementing these in Spring Boot!