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Message from discussion help with aggregation & group by
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Chuck Remes  
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 More options Nov 6 2007, 7:05 am
From: Chuck Remes <cremes.devl...@mac.com>
Date: Tue, 6 Nov 2007 06:05:54 -0600
Local: Tues, Nov 6 2007 7:05 am
Subject: Re: help with aggregation & group by
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On Nov 5, 2007, at 11:21 PM, Sharon Rosner wrote:

>> Am I best off just executing the SQL above and saving it into a
>> dataset for ruby manipulation?

> Right now yes. You can do that easily:

>  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}

This is the method I'm using right now. It's somewhat ugly but still  
very functional!

> 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

Ooh, that's pretty!

> 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?

Just opened it. Listed as Defect #88.

I'll take a stab at providing some of this functionality but it means  
learning ParseTree and probably ruby2ruby which might be a bit beyond  
my ruby capabilities right now. Don't hold your breath waiting for my  
patch... ;-)

cr


 
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