Rails - Aug 2007 - How do you calculate the max # of sales in a 5 day period?

If I''m trying to calculate the record (max) number of sales within a 5
day period, how would I do it? I''m guessing it starts with a
Sales.maximum, but being an absolute noob, I have no idea what next.

Maybe like a Sales.maximum(:group => 5.days) --- or something similar?
I''m probably completely wrong with my approach.

Any ideas?
-- 
Posted via http://www.ruby-forum.com/.

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On Aug 30, 7:02 am, Bob Sanders
<rails-mailing-l...-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:
> If I''m trying to calculate the record (max) number of sales within
a 5
> day period, how would I do it? I''m guessing it starts with a
> Sales.maximum, but being an absolute noob, I have no idea what next.
>
> Maybe like a Sales.maximum(:group => 5.days) --- or something similar?
> I''m probably completely wrong with my approach.
>
> Any ideas?
> --
> Posted viahttp://www.ruby-forum.com/.
if you have an array of daily sales, you can each_cons over it:

http://stdlib.rubyonrails.org/libdoc/enumerator/rdoc/index.html


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On 8/30/07, Bob Sanders
<rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:
>
> If I''m trying to calculate the record (max) number of sales within
a 5
> day period, how would I do it? I''m guessing it starts with a
> Sales.maximum, but being an absolute noob, I have no idea what next.
What do you mean when you say "max?" Which day of 5 specific days had
the most sales? Does your table have one row per day or one row per
sale?

Assuming you had one row per sale, then the number of sales per day
would be given by:

   select date, count(*) from sales
   group by date

To restrict to a 5-day window, you use a where clause:

   select date, count(*) from sales
   where date between ? and ?
   group by date

To get the date with the highest, you can do something like this with MySQL:

   select date, count(*) from sales
   where date between ? and ?
   group by date
   order by 2 desc
   limit 1

In AR you write that as:

   Sales.count :conditions => [''date between ? and ?'', d1,
d2],
     :group => ''date'',
     :order => ''2 desc'',
     :limit => 1

That will return an array with one element, which in turn is an array
with two elements: a date, and a number representing the count of rows
for that date.

HTH

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