Through a Join Table

Let us allow Users to follow one another. We'll need to go through a join table for the many-to-many and hence two joins to fetch this field. For this we can specify joinTable, which is the name of the intermediate join table. We also need sqlJoins, an array of two functions that generate the JOIN conditions, the first joins the parent table to the intermediate, and the second joins the intermediate to the child table.

const User = new GraphQLObjectType({
  fields: () => ({
    following: {
      description: 'Users that this user is following',
      type: new GraphQLList(User),
      joinTable: 'relationships', // this is the name of our join table
      sqlJoins: [
        // first the parent table to the join table
        (followerTable, relationTable, args) => `${followerTable}.id = ${relationTable}.follower_id`,
        // then the join table to the child
        (relationTable, followeeTable, args) => `${relationTable}.followee_id = ${followeeTable}.id`

Now we have a self-referential, many-to-many relationship.

  users { 
    id, idEncoded, email, fullName
    following { fullName }