find nonbreaking period with condition - sql

Question

There are quotas for hotels per day in a table. How to get number of days when hotel is daily available?
q_id q_hotel q_date q_value
1 1 2013-02-01 1
2 1 2013-02-02 1
3 1 2013-02-03 1
4 1 2013-02-04 0
5 1 2013-02-05 2
6 1 2013-02-06 3
7 1 2013-02-07 3
8 1 2013-02-08 2
9 1 2013-02-09 0
10 1 2013-02-10 0
11 1 2013-02-11 1
12 1 2013-02-12 1
Wanted output:
q_hotel q_date days_available
1 2013-02-01 3
1 2013-02-02 2
1 2013-02-03 1
1 2013-02-04 0
1 2013-02-05 4
1 2013-02-06 3
1 2013-02-07 2
1 2013-02-08 1
1 2013-02-09 0
1 2013-02-10 0
1 2013-02-11 2
1 2013-02-12 1
For now I can get number of days if there is zero quote after needed date exists - I find closest unavailable day and calculate dates difference.
http://sqlfiddle.com/#!12/1a64c/14
select q_hotel
,q_date
,(select extract(day from (min(B.q_date)-A.q_date)) from Table1 B where B.q_date>A.q_date
and B.q_value=0 and A.q_value<>0)
from Table1 A
But there is a problem when I don't have a zero closing date.

Answer 1

Here is a solution:
select
a.q_date
, a.q_hotel
, case
when
a.q_value = 0
then
0
else
(
select
extract
( day from
min ( b.q_date ) - a.q_date + interval '1 day'
)
from table1 b
where b.q_date >= a.q_date
and b.q_hotel = a.q_hotel
and not exists
(
select 1
from table1 c
where c.q_date = b.q_date + interval '1 day'
and b.q_hotel = a.q_hotel
and q_value <> 0
)
)
end as days_available
from table1 a