SQL DATEDIFF returns wrong result

Question

My SQL query is as below,

SELECT  CAST(-1 * DATEDIFF(hour, '21-APR-2019 11:30:00 AM', '22-APR-2019 
2:15:20 PM') % 24 AS VARCHAR) 

Output of above query:-

-3 

Expected Output :-

-2

Answer 1

This is because:

DATEDIFF(hour, '21-APR-2019 11:30:00 AM', '22-APR-2019 
2:15:20 PM')

returns 27 and not 26 .
Change to this:

SELECT  CAST(-1 * (DATEDIFF(minute, '21-APR-2019 11:30:00 AM', '22-APR-2019 
2:15:20 PM') / 60) % 24 AS VARCHAR)