What is it

Schema is a contract/promise between the server and client when exchanging data.

Schema defines a collection of types and the relationships among themeselves.

• Unified schema in GraphQL allows clients to see exactly what data is available and then request a specific subset of the data with a single optimized query.

type Starship {
  id: ID!
  name: String!
  # length takes argument of unit w/ default valueof METER
  length(unit: LengthUnit = METER): Float
}

Root Types (Entry Points)

There are two types that are special within a schema:

schema {
  query: Query
  mutation: Mutation
}

Every GraphQL service always have a query type.

• 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 queries and mutations.

Type Definitions

typeDefs is synonymous with schema.

• contains the schema definitions written as SDL (Schema Definition Language).

typeDefs can be an array of strings.

• Each string is a GraphQL schema definition.

Apollo Server will merge all the typeDefs together when starting the server.

Template Literal

You can define schema/typeDefs with a template literal with graphql-tag.

Apollo server also provides gql from @apollo/server.

const gql = require("graphql-tag");

const typeDefs = gql`
  # Schema definitions go here
`;

module.exports = typeDefs;