GraphQL

The Query and Mutation types

Most types in your schema will just be normal object types, but there are two types that are special within a schema:

schema {
  query: Query
  mutation: Mutation
}

Every GraphQL service has a query type and may or may not have a mutation type. These types are the same as a regular object type, but they are special because they define the entry point of every GraphQL query. So if you see a query that looks like:

query {
  hero {
    name
  }
  droid(id: "2000") {
    name
  }
}

output:

{
  "data": {
    "hero": {
      "name": "R2-D2"
    },
    "droid": {
      "name": "C-3PO"
    }
  }
}

That means that the GraphQL service needs to have a Query type with hero and droid fields:

type Query {
  hero(episode: Episode): Character
  droid(id: ID!): Droid
}

Mutations work in a similar way - you define fields on the Mutation type, and those are available as the root mutation fields you can call in your query.

It's important to remember that other than the special status of being the "entry point" into the schema, the Query and Mutation types are the same as any other GraphQL object type, and their fields work exactly the same way.