Counting days ...

Hi all,

A bit stuck here with something I know I can do with output / loops /
filtering in the (web)application but want to do in SQL or within PostgreSQL.

Simply said, count days of accommodation for a given time period.

E.g.

res_id 1, start_day 2008-01-25, end_day 2008-02-15, number of persons 6
res_id 2, start_day 2008-02-10, end_day 2008-02-15, number of persons 4

for the period from 2008-02-01 to 2008-02-29 these two rows would give a total
of

15 days x 6 persons + 4 days x 5 persons = 110 days

SELECT SUM(
CASE
WHEN res_start_day >= '2008-01-01' THEN
(res_end_day - res_start_day)
ELSE (res_end_day - (DATE '2008-01-01' - INTEGER '1'))
END
* group_size) AS days_in_period
FROM product_res pr
WHERE res_end_day >= '2008-01-01' AND res_end_day <= '2008-12-31';

days_in_period
----------------
68383
(1 row)

Ok, but a reservation can be of any nationality / country:

SELECT count(country_id) FROM countries;
count
-------
243
(1 row)

Country_id is also stored in the product_res table.

I would like to, or need to, get the total split into different nationalities,
like:

FI 12345
RU 9876
DE 4321
...

Anyone ?

With very best regards,

--
Aarni Ruuhimäki
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Burglars usually come in through your windows.
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