models.js

const bookshelf = require('../bookshelf')

const Definition = bookshelf.Model.extend({
  tableName: 'definitions'
})

const Player = bookshelf.Model.extend({
  tableName: 'players',
  game: () => this.belongsTo(Game, 'game.id')
})

const Game = bookshelf.Model.extend({
  tableName: 'games',
  definitions: () => this.hasMany(Definition),
  players: () => this.hasMany(Player)
})

schema.js

exports.up = knex => {
  return knex.schema
    .createTable('games', table => {
      table.increments('id').primary()
      table.string('name')
      table.timestamps()
    }).createTable('definitions', table => {
      table.increments('id').primary()
      table.string('definition')
      table.integer('game_id').references('game.id')
    }).createTable('players', table => {
      table.increments('id').primary()
      table.string('username')
      table.string('email')
      table.string('password')
      table.integer('game_id').references('game.id')
    })
}

exports.down = knex => {
  return knex.schema
    .dropTable('games')
    .dropTable('definitions')
    .dropTable('players')
}