SinatraのActiveRecordについての質問です。

Question

$ rake db:migrate

rake aborted!
ActiveRecord::ConnectionNotEstablished: No connection pool for ActiveRecord::Base
/usr/local/rvm/gems/ruby-2.2.1/gems/activerecord-4.2.4/lib/active_record/connection_adapters/abstract/connection_pool.rb:570:in `retrieve_connection'
/usr/local/rvm/gems/ruby-2.2.1/gems/activerecord-4.2.4/lib/active_record/connection_handling.rb:113:in `retrieve_connection'
/usr/local/rvm/gems/ruby-2.2.1/gems/activerecord-4.2.4/lib/active_record/connection_handling.rb:87:in `connection'
/usr/local/rvm/gems/ruby-2.2.1/gems/activerecord-4.2.4/lib/active_record/migration.rb:913:in `initialize'
/usr/local/rvm/gems/ruby-2.2.1/gems/activerecord-4.2.4/lib/active_record/migration.rb:820:in `new'
/usr/local/rvm/gems/ruby-2.2.1/gems/activerecord-4.2.4/lib/active_record/migration.rb:820:in `up'
/usr/local/rvm/gems/ruby-2.2.1/gems/activerecord-4.2.4/lib/active_record/migration.rb:798:in `migrate'
/usr/local/rvm/gems/ruby-2.2.1/gems/activerecord-4.2.4/lib/active_record/tasks/database_tasks.rb:137:in `migrate'
/usr/local/rvm/gems/ruby-2.2.1/gems/activerecord-4.2.4/lib/active_record/railties/databases.rake:44:in `block (2 levels) in <top (required)>'
Tasks: TOP => db:migrate
(See full trace by running task with --trace)

このようなエラーが出るのはなぜなのでしょうか・・・

Comments

[gouf]

どのようなファイル・コードの構成、そういった、rake コマンド以前の手順などを提示いただけないでしょうか