MS SQL datetime precision problem

Question

I have a situation where two persons might work on the same order (stored in an MS SQL database) from two different computers. To prevent data loss in the case where one wou

Answer 1

Whilst you are within SQL 2005 and before the accuracy issue will always be there, never more accurate than 1/300th of a second, or 3.33ms.

Regardless of the lack of accuracy you are programming a flawed race condition where both users can still write to the database in quick sucession but both be considered sucessful. The lack of accuracy increases the chances of it occuring, as long as the check and subsequent writes occured within the same 3-4 ms.

Any attempt to check followed by a write suffers this problem, and you either have to accept the consequences of optimistic locking, change the locking to pessemistic or implement some form of semaphore type strategy to handle the locking properly.