Convert SQL Server DateTime object to BIGINT (.Net ticks)

Question

I need to convert a DateTime type value to BIGINT type in .Net ticks format (number of 100-nanosecond intervals that have elapsed since 12:00:00 midnight, January 1, 0001).<

Answer 1

EDIT: Updated due to updated details regarding original question

To give such precision of 100ns you should execute algorithm on SQL Server 2008 using new date type - datetime2 which accuracy is 100 nanoseconds. Obviously link to an algorithm itself already provided in an other post.

DateTime.Ticks Property

A single tick represents one hundred nanoseconds or one ten-millionth of a second. There are 10,000 ticks in a millisecond.

The value of this property represents the number of 100-nanosecond intervals that have elapsed since 12:00:00 midnight, January 1, 0001, which represents DateTime.MinValue. It does not include the number of ticks that are attributable to leap seconds.

DateTime dateTime = DateTime.Now;
System.Int64 ticks = dateTime.Ticks;

Answer 2

A more performant solution might be: (note first two line are just for testing)

DECLARE @YourDate DATETIME

SET @YourDate = GETDATE()

SELECT 
(
  (
  -- seconds since 1970
  CAST(DATEDIFF(s,'1970-01-01 12:00:00',@YourDate) As BIGINT)
  )
-- seconds from 0001 to 1970 (approximate)
+ 62125920000
) 
-- make those seconds nanoseconds
* 1000000000

Given that your input date only goes down to seconds we just work it out in seconds and multiply by 1000000000 to get nanoseconds.