joining

ar.rb

@companies = Company.includes(:users).all

@companies.each do |company|
  company.users.each do |user|
    "#{company.name} #{user.name}"
  end
end

find_by_sql.rb

@companies = Company.find_by_sql <<-SQL
SELECT c.name AS company_name, u.name AS user_name
FROM companies c
INNER JOIN users u ON c.id = u.company_id
SQL

@companies.each do |company|
  "#{company.company_name} #{company.user_name}"
end

join.rb

@companies = Company.select("companies.name AS company_name, users.name AS user_name").joins(:users).all

@companies.each do |company|
  "#{company.company_name} #{company.user_name}"
end