Here's my table definition and the SQL I am running against it:

class Order < Sequel::Model(:orders)
set_schema do
   primary_key :id, :auto_increment => true
   varchar :market, :size => 12
   decimal :created_at, :elements => [15,5]
   decimal :ack, :elements => [15,5]
end
end

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));

As you may infer, the ack and created_at columns are large floating  
point numbers (seconds plus microseconds) representing time relative  
to the UNIX epoch. Is it possible to write this in Sequel and have it  
generate the correct SQL? Here's an attempt...

market = 'ICE'
Order.filter{:market => market && :ack >  
15.minutes.ago}.avg(:no_idea_what_to_do_from_here).group(:still_lost)

I need to do math (subtraction) on two columns in the result set and  
average that value. I also need access to mysql's +minute+ function  
and +unix_timestamp+ function. I looked through the code but got lost  
pretty quickly when trying to figure out how to monkey patch this in.