Person(name, dob, gender, zipcode)
Event(name, date)
Registrations(person_id, event_id, status, comment)

rails new handson

gem 'pry-rails'
gem 'better_errors'
gem 'awesome_print'
gem 'faker'

rails generate resource Person name:string dob:date gender:string zipcode:string
rails generate resource Event name:string event_date:date event_time:time
rails generate model Registration person_id:integer event_id:integer

 Event.delete_all
 Person.delete_all
 Registration.delete_all
 
 5.times do
   event_name = (Faker::Hacker.ingverb + " " + Faker::Hacker.noun + "s").capitalize
   Event.create(name: event_name, event_date: Faker::Date.between(1.year.ago, 1.day.ago), event_time: '12:00pm')
 end
 
(1..10).each do
  p = Person.create(name: Faker::Name.name,
    dob: Faker::Date.between(30.years.ago, 10.years.ago),
    gender: ['f', 'm'].sample, zipcode: Faker::Address.zip)
end

3.times do
  r = Registration.create(person_id: Person.all.sample.id, event_id: Event.all.sample.id)
end

rails db:create  # creates the database for the current env
rails db:migrate # Run latest migrations
rails db:seed    # (only) runs the db/seed.rb file
rails db:setup   # runs db:schema:load, db:seed

rails dbconsole
.help
.databases
.tables
select * from people;
select * from people where id > 1;

rails console
ActiveRecord::Base.connection.tables
Person.all
Person.where(gender: 'm')
Person.where("dob > ?", Date.new(1995))
Person.where("dob > ?", Date.new(1995)).count

p = Person.new(name: "Pito", dob: '12-12-2012', gender: 'f', zipcode: 12355)
p.new_record?
p.save
p = Person.create(name: "Amin", dob: '12-12-2014', gender: 'm', zipcode: 31231)
p.delete

 class Person < ActiveRecord::Base
   has_many :registrations
   has_many :events, through: :registrations
 end
 class Event < ActiveRecord::Base
   has_many :registrations
   has_many :people, through: :registrations
 end
 class Registration < ActiveRecord::Base
  belongs_to :person
  belongs_to :event
end

Person.find(1).registrations
Person.where(name: "Angelo Smith").first.registrations
Event.find(1).people

validates :zipcode, length: { is: 5}    # declared in model

p = Person.find(1)
p.zipcode = 1                           # invalid value
p.valid?                                # explicit check
p.save                                  # Is not permitted
p.save!                                 # Same but exception