Get distinct consecutive date ranges from overlapping date ranges

The logic is:

• at the beginning of an interval add its value to a cumulative sum
• at the end of an interval substract its value from this sum
• but in order to sweep the dateline, we'll have to collect al the (unique) date/time stamps, either start or stop.

So the point is: convert the data from a series of intervals to a series of (start/stop) events, and aggregate over these.

---

-- \i tmp.sql

create table coinsonperiod(
  id serial,
  startdate date,
  enddate date,
  coins integer
);
insert into coinsonperiod (startdate, enddate, coins) values
  ('2018-01-01','2018-01-31', 80)
, ('2018-01-07','2018-01-10', 10)
, ('2018-01-07','2018-01-31', 10)
, ('2018-01-11','2018-01-31', 5)
, ('2018-01-25','2018-01-27', 5)
, ('2018-02-02','2018-02-23', 100)
        ;

WITH changes AS (
    SELECT startdate AS tickdate , coins
            , 1 AS cover
    FROM coinsonperiod
    UNION ALL
    -- add 1 day to convert to half-open intervals
    SELECT 1+enddate AS tickdate, -1* coins
            , -1 AS cover
    FROM coinsonperiod
    )
, sumchanges  AS (
        SELECT tickdate, SUM(coins) AS change, SUM(cover) AS cover
        FROM changes
        GROUP BY tickdate
        )
, aggregated AS (
        SELECT
        tickdate AS startdate
        , lead(tickdate) over www AS enddate
        , sum(change) OVER www AS cash
          -- number of covered intervals
        , sum(cover) OVER www AS cover
        FROM sumchanges
        WINDOW www AS (ORDER BY tickdate)
        )
             -- substract one day from enddate to correct back to closed intervals
SELECT startdate, enddate-1 AS enddate, cash, cover
FROM aggregated
WHERE cover > 0
ORDER BY startdate
        ;

Looks like I found an ugly one that works

select t1.dt, t1.enddt, sum(coins)
from (
    select distinct cp1.dt, min(cp2.dt) enddt
    from ( select startdate as dt from coinsonperiod union all select enddate as dt from coinsonperiod ) cp1, 
         ( select startdate as dt from coinsonperiod union all select enddate as dt from coinsonperiod ) cp2
    where cp2.dt > cp1.dt
    group by cp1.dt
    order by cp1.dt ) t1, coinsonperiod t2
where t1.dt between t2.startdate and t2.enddate
and t1.enddt between t2.startdate and t2.enddate
group by t1.dt, t1.enddt

Output:

dt         |enddt      |sum |
-----------|-----------|----|
2018-01-01 |2018-01-07 |80  |
2018-01-07 |2018-01-10 |100 |
2018-01-10 |2018-01-11 |90  |
2018-01-11 |2018-01-25 |95  |
2018-01-25 |2018-01-27 |100 |
2018-01-27 |2018-01-31 |95  |
2018-02-02 |2018-02-23 |100 |

Only difference with your output is that I suppose you forgot the interval between 01/10 and 01/11