How to add a value to a field from the database?

Question

PHP

How to add a value to a table field? For example, the number 50 is stored there, and when replenishing the balance, a number, for example 100, should be added. Of course, you can first take the balance value, add and update, but I would like to immediately add the desired number.

Answer 1

You display the current balance from the database, add to the current balance by how much you need to increase it.
The resulting number is entered into the database.

Answer 2

As an option, put the replenishment in the hotel table. At replenishment you interpose simply record in this table.