For instance, if you have an API with the functions:
item# = add_item(description, price, color) record_sale(item#, quantity, customer#)
record_sale(item#, quantity, customer#, price=NULL)
But you already have sales data without a price, so you need to migrate it by copying the current item prices over.
And if one of three applications doesn't support the new API, you need to offer the old API as well and it would just use the default all of the time.
That sounds pretty much like a schema to me. What's the difference?
For instance, if you have an API with the functions:
So let's see what happens when you need to make a change. For instance, you might decide that an item could be discounted (a new feature); so you need to record the price at the time of sale: and if the price is NULL, you default to the current item price.But you already have sales data without a price, so you need to migrate it by copying the current item prices over.
And if one of three applications doesn't support the new API, you need to offer the old API as well and it would just use the default all of the time.
That sounds pretty much like a schema to me. What's the difference?