If someone is editing data belonging to one table and another comes along and starts to edit other data belonging to that same table - what I would like to do is lock it read only for the second user - where he/she cannot change it - sort of what Excel does when two people open the same document - is that possible? Then if the first user leaves - the locking is removed for the second user - where he/she can change it?
Sure there is a lot online for record-row level locking, column locking would slow performance and then you get into user-permisions. But this is special to where you want the locking to occur only on the second user (or third, fourth) temporarily and return when there is one user only accessing the table.
Second question - should this not be done at database level but merely only software front-end?