while true this is not what I mean.

if your goal is to transfer 10 dollars for account A to account B but only if account A balance is larger than 10 dollars.

You have to update account A to be 10 dollars less

and

you have to update account B to be 10 dollars more.

you can read both account a keep track of current version number for each.

then do

"UPDATE Accounts SET Balance = CASE AccountID WHEN 1 THEN Balance - 10 WHEN 2 THEN Balance + 10 END WHERE (AccountID, version) IN ((1,v1), (2,v2))"

But if using Read Uncommited isolation level I am not sure this UPDATE would actually lock both row until commit.