MySQL Number of Days inside a DateRange, inside a month (Booking Table)

Question

I\'m attempting to create a report for an accommodation service with the following information:

Number of Bookings (Easy, use the COUNT function)
Revenue Amount          


        

Answer 1

You're on the right lines. You need to join your query with a table of the months for which you want data, which can either be permanent or (as shown in my example below) created dynamically in a UNION subquery:

SELECT   YEAR(month.d),
         MONTHNAME(month.d),
         SUM(1 + DATEDIFF( -- add 1 because start&finish on same day is still 1 day
           LEAST(Checkout, LAST_DAY(month.d)), GREATEST(Checkin, month.d)
         )) AS days
FROM     bookingdata
  RIGHT JOIN (
                   SELECT 20110101 AS d
         UNION ALL SELECT 20110201 UNION ALL SELECT 20110301
         UNION ALL SELECT 20110401 UNION ALL SELECT 20110501
         UNION ALL SELECT 20110601 UNION ALL SELECT 20110701
         UNION ALL SELECT 20110801 UNION ALL SELECT 20110901
         UNION ALL SELECT 20111001 UNION ALL SELECT 20111101
         UNION ALL SELECT 20111201
  ) AS month ON
             Checkin <= LAST_DAY(month.d)
         AND month.d <= Checkout
GROUP BY month.d

See it on sqlfiddle.