A sample of using sequel and sinatra together.

sinatra_sequel.rb

require 'yaml'
require 'sinatra/base'
require 'sequel_core'

class MyApp < Sinatra::Base
  configure do
    DB = Sequel.connect YAML.load(File.read(__FILE__).split("__END__\n")[-1])[ENV['RACK_ENV'] || 'production']
    Sequel::Mysql.convert_tinyint_to_bool = false
  end

  # routes any anything else come below
end

__END__
---
development: &base
  adapter: mysql
  host: localhost
  user: mysql-user # username is also acceptable
  password: secret
  port: 3363
  #socket: /tmp/mysqld/mysqld.sck
  encoding: utf8
  compress: false
  timeout: 300
  auto_is_null: false

production:
  <<: *base
  host: another_host
  user: puser
  password: ******