Comparing date ranges

Question

In MySQL, If I have a list of date ranges (range-start and range-end). e.g.

10/06/1983 to 14/06/1983
15/07/1983 to 16/07/1983
18/07/1983 to 18/07/1983


        

Answer 1

In your expected results you say

06/06/1983 to 18/06/1983 = IN LIST

However, this period does not contain nor is contained by any of the periods in your table (not list!) of periods. It does, however, overlap the period 10/06/1983 to 14/06/1983.

You may find the Snodgrass book (http://www.cs.arizona.edu/people/rts/tdbbook.pdf) useful: it pre-dates mysql but the concept of time hasn't changed ;-)

Answer 2

I created function to deal with this problem in MySQL. Just convert the dates to seconds before use.

DELIMITER ;;

CREATE FUNCTION overlap_interval(x INT,y INT,a INT,b INT)
RETURNS INTEGER DETERMINISTIC
BEGIN
DECLARE
    overlap_amount INTEGER;
    IF (((x <= a) AND (a < y)) OR ((x < b) AND (b <= y)) OR (a < x AND y < b)) THEN
        IF (x < a) THEN
            IF (y < b) THEN
                SET overlap_amount = y - a;
            ELSE
                SET overlap_amount = b - a;
            END IF;
        ELSE
            IF (y < b) THEN
                SET overlap_amount = y - x;
            ELSE
                SET overlap_amount = b - x;
            END IF;
        END IF;
    ELSE
        SET overlap_amount = 0;
    END IF;
    RETURN overlap_amount;
END ;;

DELIMITER ;

Answer 3

Look into the following example. It will helpful for you.

    SELECT  DISTINCT RelatedTo,CAST(NotificationContent as nvarchar(max)) as NotificationContent,
                ID,
                Url,
                NotificationPrefix,
                NotificationDate
                FROM NotificationMaster as nfm
                inner join NotificationSettingsSubscriptionLog as nfl on nfm.NotificationDate between nfl.LastSubscribedDate and isnull(nfl.LastUnSubscribedDate,GETDATE())
  where ID not in(SELECT NotificationID from removednotificationsmaster where Userid=@userid) and  nfl.UserId = @userid and nfl.RelatedSettingColumn = RelatedTo

Answer 4

If your RDBMS supports the OVERLAP() function then this becomes trivial -- no need for homegrown solutions. (In Oracle it apparantly works but is undocumented).