$ sequel -E sqlite:/
Your database is stored in DB...
irb(main):001:0> DB.create_table :test do
irb(main):002:1*   primary_key :id
irb(main):003:1>   String :username, :unique => true
irb(main):004:1>   String :password
irb(main):005:1> end
I, [2009-09-06T11:47:06.099299 #20103]  INFO -- : CREATE TABLE `test` (`id` integer PRIMARY KEY AUTOINCREMENT, `username` varchar(255) UNIQUE, `password` varchar(255))
=> []
irb(main):006:0> test = DB[:test]
=> #<Sequel::SQLite::Dataset: "SELECT * FROM `test`">
irb(main):007:0> test.insert(:username => 'foo', :password => 'foo')
I, [2009-09-06T11:47:06.104020 #20103]  INFO -- : INSERT INTO `test` (`password`, `username`) VALUES ('foo', 'foo')
=> 1
irb(main):008:0> print "#{test.select(:username).first()[:username]}\n"
I, [2009-09-06T11:47:06.105782 #20103]  INFO -- : SELECT `username` FROM `test` LIMIT 1
foo
=> nil
irb(main):009:0> print "#{test.filter(:username => 'foo')}\n"
#<Sequel::SQLite::Dataset:0x211366448>
=> nil