So today a professor told us that when the database has to make an update, internally (at low level) it makes a delete and then an insert with the updated fields. He then said that this is something made across all databases and then I started a discussion telling that I thought that it had no sense but I didn't had enough resources to support my position. He seems to know a lot but I can't understand why would dbs do that.
I mean, I know that if you update a field and you need more space for that row, then it may delete the row physically and put it at the end with the new data. But if for example you reduce the space used, why would it delete and re insert it at the end?
Is this even true? What are the benefits?