Number of days between two given dates

问题:

How do I calculate number of days between the to dates strictly using HQL alone.

supposing Current_Date and Expiry_Date are two dates fetched from database. I want to calculate days between Current_Date and Expiry_Date.

Also, How will I handle, if any of the value is null ?

回答1:

DECLARE @startdate datetime2 = '2013-12-05 12:10:09.3312722';
DECLARE @enddate datetime2 = '2013-12-04 12:10:09.3312722'; 
SELECT DATEDIFF(day, isnull(@startdate,GetDate()), isnull(@enddate,GetDate()));

回答2:

I figured an solution for my issue.

(extract(doy from bp.qhrIqamaexpirDate)-extract(doy from now()))

doy represents The day of the year (1 - 365/366).

bp.qhrIqamaexpirDate : 2013-02-28 00:00:00.0

now() : 2013-03-14 14:53:12.051562

extract(doy from  bp.qhrIqamaexpirDate) : 59, extract(doy from now()) : 73