sql = "select market, minute(from_unixtime(ack)) AS minute,
round(avg((ack -
  created_at) * 1000), 2) AS ack_average from orders  where 'ack' >
  (UNIX_TIMESTAMP(now()) - (15 * 60) and 'market' = 'ICE' group by
  minute(from_unixtime(ack));"

  dataset = DB[sql]
  dataset.each {|r| p r}

I've played with it a bit and right now, field quoting in the mysql
adapter is broken, so you can't use any functions or formulas in
#select, #group etc. Ultimately our goal should look like this:

  market = 'ICE'
  ack_stamp = 15.minutes.ago
  Order.query do
    select do
      :market,
      :minute[:from_unixtime[:ack]].AS :minute
      :round[:avg[(:ack - :created_at) * 1000], 2].AS :ack_average
    end
    where do
      :ack > ack_stamp
      :market == market
    end
    group_by :minute[:from_unixtime[:ack]]
  end

With the help of ParseTree I think it's possible to do that, and also
to fix field quoting. Can you please open an issue for this?