Hvordan finder jeg det samlede antal brugte dage i en måned?

Testdata :

CREATE TABLE your_table ( usr, start_date, end_date ) AS (
  SELECT 'A', DATE '2017-06-01', DATE '2017-06-03' FROM DUAL UNION ALL
  SELECT 'B', DATE '2017-06-02', DATE '2017-06-04' FROM DUAL UNION ALL -- Overlaps previous
  SELECT 'C', DATE '2017-06-06', DATE '2017-06-06' FROM DUAL UNION ALL
  SELECT 'D', DATE '2017-06-07', DATE '2017-06-07' FROM DUAL UNION ALL -- Adjacent to previous
  SELECT 'E', DATE '2017-06-11', DATE '2017-06-20' FROM DUAL UNION ALL
  SELECT 'F', DATE '2017-06-14', DATE '2017-06-15' FROM DUAL UNION ALL -- Within previous
  SELECT 'G', DATE '2017-06-22', DATE '2017-06-25' FROM DUAL UNION ALL
  SELECT 'H', DATE '2017-06-24', DATE '2017-06-28' FROM DUAL UNION ALL -- Overlaps previous and next
  SELECT 'I', DATE '2017-06-27', DATE '2017-06-30' FROM DUAL UNION ALL
  SELECT 'J', DATE '2017-06-27', DATE '2017-06-28' FROM DUAL;          -- Within H and I          

Forespørgsel :

SELECT SUM( days ) AS total_days
FROM   (
  SELECT dt - LAG( dt ) OVER ( ORDER BY dt ) + 1 AS days,
         start_end
  FROM   (
    SELECT dt,
           CASE SUM( value ) OVER ( ORDER BY dt ASC, value DESC, ROWNUM ) * value
             WHEN 1 THEN 'start'
             WHEN 0 THEN 'end'
           END AS start_end
    FROM   your_table
    UNPIVOT ( dt FOR value IN ( start_date AS 1, end_date AS -1 ) )
  )
  WHERE start_end IS NOT NULL
)
WHERE start_end = 'end';

Output :

TOTAL_DAYS
----------
        25

Forklaring :

SELECT dt, value
FROM   your_table
UNPIVOT ( dt FOR value IN ( start_date AS 1, end_date AS -1 ) )

Dette vil UNPIVOT tabellen, så start- og slutdatoerne er i samme kolonne (dt ) og får en tilsvarende værdi på +1 for en start og -1 for en slutdato.

SELECT dt,
       SUM( value ) OVER ( ORDER BY dt ASC, value DESC, ROWNUM ) AS total,
       value
FROM   your_table
UNPIVOT ( dt FOR value IN ( start_date AS 1, end_date AS -1 ) )

Giver start- og slutdatoerne og den kumulative sum af de genererede værdier. Starten af ​​et interval vil altid have value=1 og total=1 og slutningen af ​​et interval vil altid have total=0 . Hvis en dato er midtvejs i et interval, vil den enten have total>1 eller value=-1 og total=1 . Ved at bruge dette, hvis du multiplicerer value og total så er starten på et interval, når value*total=1 og slutningen af ​​et interval er, når value*total=0 og enhver anden værdi angiver en dato, der er midtvejs i et interval.

Hvilket er, hvad dette giver:

SELECT dt,
       CASE SUM( value ) OVER ( ORDER BY dt ASC, value DESC, ROWNUM ) * value
         WHEN 1 THEN 'start'
         WHEN 0 THEN 'end'
       END AS start_end
FROM   your_table
UNPIVOT ( dt FOR value IN ( start_date AS 1, end_date AS -1 ) )

Du kan derefter bortfiltrere datoerne for start_end er NULL hvilket vil efterlade dig med en tabel med skiftende start og end rækker, som du kan bruge LAG for at beregne antallet af dages forskel:

SELECT dt - LAG( dt ) OVER ( ORDER BY dt ) + 1 AS days,
       start_end
FROM   (
  SELECT dt,
         CASE SUM( value ) OVER ( ORDER BY dt ASC, value DESC, ROWNUM ) * value
           WHEN 1 THEN 'start'
           WHEN 0 THEN 'end'
         END AS start_end
  FROM   your_table
  UNPIVOT ( dt FOR value IN ( start_date AS 1, end_date AS -1 ) )
)
WHERE start_end IS NOT NULL

Alt du skal gøre derefter er at SUM alle forskellene for end - start; hvilket giver forespørgslen ovenfor.