What are the three main operation types in GraphQL?

GraphQL has three operation types: query for reading, mutation for writing, and subscription for real-time updates. Each starts at its own root type in the schema, Query, Mutation or Subscription, whose fields are that operation's entry points.

1. A query reads data. The server can resolve its fields in parallel.
2. A mutation writes data. Its top-level fields run one after another, so two writes in one request never race.
3. A subscription keeps a long-lived request open, and the server pushes new data each time an event happens.

query GetUser {
  user(id: "123") { name }
}

mutation CreateUser {
  createUser(input: { name: "John" }) {
    name
  }
}

subscription UserUpdates {
  userUpdated(id: "123") {
    name
  }
}