Precision of SQL Getdate?

Question

I am experimenting with a program that inserts data into an SQL 2005 Server database (on XP SP3) at high rate of speed. (This is for collecting timing data so I can evalua

Answer 1

DATETIME is stored as 2 integers. One representing the date part and the other the time part (number of ticks after midnight) each tick is 1/300 of a second so it has at least a theoretical precision of 3.3 milliseconds.

I just tried running this on my machine

declare @d  varchar(24)

while 1=1 
begin
set @d=CONVERT(VARCHAR(24), GETDATE(), 113)
raiserror('%s',0,1, @d) with nowait
end

And got a fairly lengthy run where it did go up one tick at a time so I don't think there can be any inherent limitation that prevents it achieving that.

01 Aug 2010 00:56:53:913
...
01 Aug 2010 00:56:53:913
01 Aug 2010 00:56:53:917
...
01 Aug 2010 00:56:53:917
01 Aug 2010 00:56:53:920
...
01 Aug 2010 00:56:53:920
01 Aug 2010 00:56:53:923

Regarding your query about GetDate() precision in SQL Server 2008 this is the same as for SQL2005. sysdatetime is meant to have higher precision. I just tried running the following and was surprised by the discrepancy between the two results.

SET NOCOUNT ON

CREATE TABLE #DT2(
[D1] [datetime2](7) DEFAULT (getdate()),    
[D2] [datetime2](7) DEFAULT (sysdatetime())
) 
GO

INSERT INTO #DT2
          DEFAULT  VALUES
GO 100

SELECT DISTINCT [D1],[D2],DATEDIFF(MICROSECOND, [D1], [D2]) AS MS
 FROM #DT2

Results

D1                           D2                              MS
----------------------------    -----------------------      ------
2010-08-01 18:45:26.0570000   2010-08-01 18:45:26.0625000     5500
2010-08-01 18:45:26.0600000   2010-08-01 18:45:26.0625000     2500
2010-08-01 18:45:26.0630000   2010-08-01 18:45:26.0625000     -500
2010-08-01 18:45:26.0630000   2010-08-01 18:45:26.0781250     15125
2010-08-01 18:45:26.0670000   2010-08-01 18:45:26.0781250     11125
2010-08-01 18:45:26.0700000   2010-08-01 18:45:26.0781250     8125