Don't have to keep transaction open. What I do is:

1. Select next job

2. Update status to executing where jobId = thatJob and status is pending

3. If previous affected 0 rows, you didn't get the job, go back to select next job

If you have "time to select" <<< "time to do" this works great. But if you have closer relationship you can see how this is mostly going to have contention and you shouldn't do it.