Re: Counting days ...

Aarni Ruuhimäki wrote:
>> 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,

#6 and #9 are the same. You missed these:

a start_day before period_start, end_day before period_start
b start_day = period_start, end_day = period_start
c start_day = period_start, end_day after period_end
d start_day = period_end, end_day = period_end
e start_day = period_end, end_day after period_end
f start_day after period_end, end_day after period_end

Granted, a & f should not match where clause; but then groups 10,c,e
don't meet your where clause either. Your where clause should probably be:

WHERE group_id = 1 AND (res_start_day >= '2007-01-01' AND res_end_day <=
'2008-12-31')

Are you sure that your database does not have any rows where start_day
is after end_day? These rows could certainly skew results.

I would suggest that you identify a few rows that meet each of these
conditions. Change the where clause to select rows in one group at a
time. You might consider using a unique row identifier in where clause
during these tests to make sure you are processing the rows you think
you are. When all test cases work properly; then run your generalized
query again.