GraphQL Queries and Mutations

Introduction

GraphQL is a query language for APIs that allows clients to request the data they need, making it a powerful alternative to REST. This lesson covers the core aspects of GraphQL queries and mutations.

GraphQL Queries

Queries in GraphQL are used to fetch data from the server. A query can specify exactly what data is needed and in what shape.

Basic Query Structure

{
    users {
        id
        name
        email
    }
}

This query fetches a list of users, retrieving their ids, names, and emails.

Using Variables in Queries

Variables can be used to make queries dynamic:

query getUser($id: ID!) {
    user(id: $id) {
        name
        email
    }
}

In this example, the $id variable is passed when executing the query, allowing for flexibility.

GraphQL Mutations

Mutations are used to modify server-side data. Unlike queries, mutations can create, update, or delete data.

Basic Mutation Structure

mutation createUser($name: String!, $email: String!) {
    createUser(name: $name, email: $email) {
        id
        name
        email
    }
}

This mutation creates a new user and returns the newly created user's details.

Using Variables in Mutations

Similar to queries, variables can be used in mutations:

mutation updateUser($id: ID!, $name: String) {
    updateUser(id: $id, name: $name) {
        id
        name
    }
}

Best Practices

• Use descriptive names for queries and mutations.
• Limit the size of responses by only requesting necessary fields.
• Implement caching to optimize performance.
• Utilize fragments for reusability in queries.
• Monitor and log all GraphQL operations for troubleshooting.

FAQ