how to get last date of today in datetime datatype?

Question

select dateadd(s, -1, dateadd(month, datediff(month, 0, getdate())+1,0))

when i execute this query, it gives '2012-01-30 23:59:59.000'. I donno how to get it as '2012-01-30 23:59:59.997'. If anybody Know, please say.

thanking you!!!

Answer 1

Why on earth do you need the last possible value of today? Stop using BETWEEN; it is much easier (and much more reliable, and consistent across various date/time data types) to use an open ended range:

DECLARE @today SMALLDATETIME;

SET @today = DATEADD(DAY, DATEDIFF(DAY, '20000101', GETDATE()), '20000101');

SELECT ... FROM ...
WHERE date_column >= @today
AND date_column < DATEADD(DAY, 1, @today);

The problem with what you're doing is that the data type can affect what happens. If the underlying data type is SMALLDATETIME, it rounds up; if the underlying data type is DATETIME or DATETIME2, subtracting a second is not going to capture all of the data from that day. This is actually one of my favorite slides in my T-SQL : Bad Habits and Best Practices talk. For a lot more details, please read these blog posts:

What do BETWEEN and the devil have in common?

Bad Habits to Kick : mis-handling date / range queries