select

require 'sdbm'

SDBM.open 'my_database' do |db|
  db['apple'] = 'fruit'
  db['pear'] = 'fruit'
  db['spinach'] = 'vegetable'

  veggies = db.select do |key, value|
    value == 'vegetable'
  end #=> [["apple", "fruit"], ["pear", "fruit"]]
end