Very basic question - does a session that gets there first complete before ...

the 2nd begins?

If 2 users are selecting the 20 lowest sequenced records from the same table with aview to updating them (so they'll be selected for update with NOWAIT), Does the 1st user to issue the SELECT get nos 1-20 or is it possible for User 2 to also begin selecting from the same table at the same time? I think not but need reassurance.

I want User1 to get 1-20 and User2 to get 21-40. And not User 1 to get (1,2,5,6,7,10,12 etc) and user2 to get (3,4,8,9,11,13, etc).