SQL how to increase or decrease one for a int column in one command

Question

I have an Orders table which has a Quantity column. During check in or check out, we need to update that Quantity column by one. Is there a way to do this in one action or w

Answer 1

UPDATE Orders Order
SET Order.Quantity =  Order.Quantity - 1
WHERE SomeCondition(Order)

As far as I know there is no build-in support for INSERT-OR-UPDATE in SQL. I suggest to create a stored procedure or use a conditional query to achiev this. Here you can find a collection of solutions for different databases.