app/controllers/tables_arrangements_controller.rb

@@ -2,10 +2,13 @@
 
 class TablesArrangementsController < ApplicationController
   def index
-    render json: TablesArrangement.all.order(discomfort: :asc).limit(10)
+    render json: TablesArrangement.all.order(discomfort: :asc).limit(10).as_json(only: %i[id discomfort])
   end
 
   def show
-    render json: TablesArrangement.find(params[:id])
+    Seat.joins(:guest).where(tables_arrangement_id: params[:id])
+        .pluck(:table_number, Arel.sql("guests.first_name || ' ' ||guests.last_name "))
+        .group_by(&:first).transform_values { |table| table.map(&:last) }
+        .then { |result| render json: result }
   end
 end

app/models/tables_arrangement.rb

@@ -2,4 +2,5 @@
 
 class TablesArrangement < ApplicationRecord
   has_many :seats
+  has_many :guests, through: :seats
 end