Introduction to GraphQL

GraphQL is a query language for APIs and a runtime for executing those queries.

What is GraphQL?

GraphQL provides a complete description of the data in your API, giving clients the power to ask for exactly what they need.

Why GraphQL?

Ask for what you need: Get exactly the data you request
Single request: Get many resources in one query
Type system: Strong typing with schema
Introspection: Query the schema itself

GraphQL vs REST

GraphQL	REST
Single endpoint	Multiple endpoints
Client specifies data	Server determines response
No over/under-fetching	Often over/under-fetches

Basic Query

graphql

query {
  user(id: "1") {
    name
    email
    posts {
      title
    }
  }
}

Schema Definition

graphql

type User {
  id: ID!
  name: String!
  email: String!
  posts: [Post!]!
}

type Post {
  id: ID!
  title: String!
  content: String
  author: User!
}

type Query {
  user(id: ID!): User
  users: [User!]!
}