How do you lock tables in SQL Server 2005, and should I even do it?

Question

This one will take some explaining. What I\'ve done is create a specific custom message queue in SQL Server 2005. I have a table with messages that contain timestamps for both a

Answer 1

Instead of explicit locking, which is often escalated by SQL Server to higher granularity than desired, why not just try this approach:

declare @MessageId uniqueidentifier
select top 1 @MessageId = ActionMessageId from UnacknowledgedDemands

update ActionMessages
  set AcknowledgedTime = getdate()
  where ActionMessageId = @MessageId and AcknowledgedTime is null

if @@rowcount > 0
  /* acknoweldge succeeded */
else
  /* concurrent query acknowledged message before us,
     go back and try another one */

The less you lock - the higher concurrency you have.