PRINT DATEDIFF(DAY, '1/1/2011', '3/1/2011')
will give you what you're after.
This gives the number of times the midnight boundary is crossed between the two dates. You may decide to need to add one to this if you're including both dates in the count - or subtract one if you don't want to include either date.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…