Mysql change number in column

Question

Here is an easy question for someone. When using mysql, how do you increase or decrease the number in a particular cell by a specified amount with a single query. For example i have a product table with 5 x product a. I sell 1 item and i want to update the field. I want to do it with one query, not get the number add to it and then update(I know how to do that) Thanks Andrew

Answer 1

UPDATE tbl SET col=col+1 WHERE id=1234

Answer 2

UPDATE Product SET Quantity = Quantity - 1 WHERE Id = xxx

Answer 3

update products set amount = amount + 1 where productId = 12345

If you are using prepared statements you can replace the amount to add as well as the product id with placeholders