Using SQL Server as a DB queue with multiple clients

Question

Given a table that is acting as a queue, how can I best configure the table/queries so that multiple clients process from the queue concurrently?

For example, the ta

Answer 1

One way is to mark the row with a single update statement. If you read the status in the where clause and change it in the set clause, no other process can come in between, because the row will be locked. For example:

declare @pickup_id int
set @pickup_id = 1

set rowcount 1

update  YourTable
set     status = 'picked up'
,       @pickup_id = id
where   status = 'new'

set rowcount 0

return @pickup_id

This uses rowcount to update one row at most. If no row was found, @pickup_id will be -1.