query on datediff function

Hi,

I am trying to use DataDiff function and I have used the following queries:

1.

select datediff(ms, '2007-05-18 19:35:07.320','2007-05-18 19:35:07.320') as test

Expected Result: 0 milliseconds

Actual Result: 0 milliseconds

2.

select datediff(ms, '2007-05-18 19:35:07.320','2007-05-18 19:35:07.321') as test

Expected Result: 1 milliseconds

Actual Result: 0 milliseconds

3.

select datediff(ms, '2007-05-18 19:35:07.320','2007-05-18 19:35:07.322') as test

Expected Result: 2 milliseconds

Actual Result: 3 milliseconds

4.

select datediff(ms, '2007-05-18 19:35:07.320','2007-05-18 19:35:07.323') as test

Expected Result: 3 milliseconds

Actual Result: 3 milliseconds

5.

select datediff(ms, '2007-05-18 19:35:07.320','2007-05-18 19:35:07.324') as test

Expected Result: 4 milliseconds

Actual Result: 3 milliseconds

6.

select datediff(ms, '2007-05-18 19:35:07.320','2007-05-18 19:35:07.325') as test

Expected Result: 5 milliseconds

Actual Result: 6 milliseconds

7.

select datediff(ms, '2007-05-18 19:35:07.320','2007-05-18 19:35:07.326') as test

Expected Result: 6 milliseconds

Actual Result: 6 milliseconds

8.

select datediff(ms, '2007-05-18 19:35:07.320','2007-05-18 19:35:07.327') as test

Expected Result: 7 milliseconds

Actual Result: 6 milliseconds

9.

select datediff(ms, '2007-05-18 19:35:07.320','2007-05-18 19:35:07.328') as test

Expected Result: 8 milliseconds

Actual Result: 6 milliseconds

10.

select datediff(ms, '2007-05-18 19:35:07.320','2007-05-18 19:35:07.329') as test

Expected Result: 9 milliseconds

Actual Result: 10 milliseconds

Does any one know, why datediff does not return the Expected Result? There does not seem to be any consistency.

Thanks,

Tim

hi Tim,

this is becouse the actual max accuracy of the datetime data type, up to 3.33 milliseconds.. so results can be "rounded"..

regards