Learning the fundamentals of GraphQL

GraphQL APIs contain three important root types – query, mutation, and subscription. These are all defined in the GraphQL schema using special SDL syntax.

GraphQL provides a single endpoint that returns the JSON response based on the request, which can be a query, a mutation, or a subscription.

First, let’s understand queries.

Exploring the Query type

The Query type is used for reading operations that fetch information from the server. A single Query type can contain many queries. Let’s write a query using SDL to retrieve the logged-in user, as shown in the following GraphQL schema:

type Query {  me: LogginInUser
  # You can add other queries here
}
type LoggedInUser {
  id: ID
  accessToken: String
  refreshToken: String
  username: String
}

Here, you have done two things:

• You have defined the query root of the GraphQL interface, which contains...