CODEWITHSUNDEEP
sqlpostgresqldate-rangecontinuous
Rob
Rob

Reputation: 1

PostgreSQL Price for multiple date ranges

I have the following table of rates for given date range.

I want to write a sql query (PostgreSQL) to get the sum of prices for a give period if it's a continuous period..for example:

if I specify 2011-05-02 to 2011-05-09 on the first set the sum of the 6 rows should be returned,

but

if i specify 2011-05-02 to 2011-05-011 on the second set nothing should be returned.

My problem is that I don't know how to determine if a date range is continuous...can you please help? Thanks a lot

case 1: sum expected

 price       from_date      to_date
------    ------------  ------------
   1.0      "2011-05-02"  "2011-05-02"
   2.0      "2011-05-03"  "2011-05-03"
   3.0      "2011-05-04"  "2011-05-05"
   4.0      "2011-05-05"  "2011-05-06"
   5.0      "2011-05-06"  "2011-05-07"
   4.0      "2011-05-08"  "2011-05-09"

case 2: no results expected

 price       from_date      to_date
------    ------------  ------------
   1.0      "2011-05-02"  "2011-05-02"
   2.0      "2011-05-03"  "2011-05-03"
   3.0      "2011-05-07"  "2011-05-09"
   4.0      "2011-05-09"  "2011-05-011"

I do not have overlapping rates date ranges.

Upvotes: 0

Views: 1728

Answers (3)

Denis de Bernardy
Denis de Bernardy

Reputation: 78523

I think you need to combine window functions and CTEs:

WITH
raw_rows AS (
SELECT your_table.*,
       lag(to_date) OVER w as prev_date,
       lead(from_date) OVER w as next_date
FROM your_table
WHERE ...
WINDOW w as (ORDER by from_date, to_date)
)
SELECT sum(stuff)
FROM raw_rows
HAVING bool_and(prev_date >= from_date - interval '1 day' AND
                next_date <= to_date + interval '1 day');

http://www.postgresql.org/docs/9.0/static/tutorial-window.html

http://www.postgresql.org/docs/9.0/static/queries-with.html

Upvotes: 0

user330315
user330315

Reputation:

Not sure I understood the question completely, but what about this:

select * 
from prices
where not exists (
  select 1 from (
     select from_date - lag(to_date) over (partition by null order by from_date asc) as days_diff
     from prices
     where from_date >= DATE '2011-05-01' 
       and to_date < DATE '2011-07-01'
  ) t 
  where coalesce(days_diff, 0) > 1
) 
order by from_date

Upvotes: 1

bobflux
bobflux

Reputation: 11581

Here's a rather fonky way to solve it :

WITH RECURSIVE t AS (
  SELECT * FROM d WHERE '2011-05-02' BETWEEN start_date AND end_date 
  UNION ALL
  SELECT d.* FROM t JOIN d ON (d.key=t.key AND d.start_date=t.end_date+'1 DAY'::INTERVAL)  
     WHERE d.start_date <= '2011-05-09') 
  SELECT sum(price), min(start_date), max(end_date) 
  FROM t 
  HAVING min(start_date) <= '2011-05-02' AND max(end_date)>= '2011-05-09';

Upvotes: 0

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