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Re: Counting days ...

From: Aarni Ruuhimäki <aarni(at)kymi(dot)com>
To: pgsql-sql(at)postgresql(dot)org
Cc: Steve Crawford <scrawford(at)pinpointresearch(dot)com>
Subject: Re: Counting days ...
Date: 2008-03-14 13:04:54
Message-ID: 200803141504.54211.aarni@kymi.com (view raw or flat)
Thread:
Lists: pgsql-sql
>
> Check my work, but I think the sum part of the query simply becomes:
>
> sum (
>   (
>   date_smaller(res_end_day, '2008-02-29'::date) -
>   date_larger(res_start_day, '2008-01-31'::date)
>   ) * group_size
> )
>
> Basically remove the "+1" so we don't include both start and end dates
> but move the start base back one day so anyone starting prior to Feb 1
> gets the extra day added.
>
> Cheers,
> Steve

Thanks Steve,

I'm not sure if I quite grasped this. It gives a bit funny results:

SELECT sum ((date_smaller(res_end_day, '2007-12-31'::date) - 
date_larger(res_start_day, '2006-12-31'::date)) * group_size) AS 
days_in_period,
c.country_name AS country
FROM product_res pr
LEFT JOIN countries c ON pr.country_id = c.country_id
WHERE group_id = 1 AND res_end_day >= '2007-01-01' AND res_end_day <= 
'2008-12-31' group by pr.country_id, c.country_name;
 days_in_period |      country
----------------+--------------------
        -441137 |
            -30 | Germany
            -28 | Estonia
             60 | Bulgaria
         -25003 | Russian Federation
        -207670 | Suomi
            256 | Ukraine
          -6566 | Latvia
           -280 | United States
          -1889 | Switzerland
            114 | Lithuania
             36 | Norway
            -66 | Sweden
            170 | Kazakhstan
             72 | Belarus
(15 rows)

Anyway, I have to rethink and elaborate the query. I know that it will usually 
be on a monthly or yearly basis, but a reservation can actually be any of the 
following in relation to the given (arbitrary) period:

1. start_day before period_start, end_day = period_start

2. start_day before period_start, end_day in period

3. start_day before period_start, end_day = period_end

4. start_day = period_start, end_day in period

5. start_day in period, end_day in period

6. start_day = period_start, end_day = period_end

7. start_day in period, end_day = period_end

8. start_day in period, end_day after period_end

9. start_day = period_start, end_day = period_end

10 start_day before period_start, end_day after period_end

Hmm ...

Best regards,
-- 
Aarni Ruuhimäki
---
Burglars usually come in through your windows.
---

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