"it will increase/decrease the revenue column amount for each transaction."

That is a terrible idea! Two transactions come in at the same time, one is a new sale and the other is reversing a sale. They each happen simultaneously, therefore either the transaction amount is too high or too low, or you are forced to lock the row when updating the column. You would be far better off having a salesperson_id column on a detail table with everything sold. Thus two products can be sold or returned at the same time without having to do locking and without one change over writing another. Beside when you update the column with each sale how do you go back and report the detail. You are either keeping track of the same data in two different place or creating data that can't be verified.