Set time portion of a datetime variable

Question

I am working on a query that will be an automated job. It needs to find all the transactions between 8 PM and 8 PM for the last day. I was thinking of doing something like

Answer 1

DECLARE @start_date DATETIME
DECLARE @end_date DATETIME

SET @start_date = DATEADD(hour, 20, DATEDIFF(DAY, 2, GETDATE()))
SET @end_date = @start_date + 1

select @start_date, @end_date