Question

I’m currently designing a database for my company’s website. I would like to create a table which will hold information (logic) about our discounts so that I can just call a function with a discountID and my php code will calculate the new price. My question is, every discount has different logic. ex. 10% off, $10 off, by one get one free, buy 3 get 50% off…

How can I store this in the database so that my code can calculate the discount on its own?

Answer 1

A database does not store logic – only data. Split this into three fields:

• discount amount (int)
• discount type (enum; possible values: ‘percent’, ‘amount’)
• buy one get N free (int; the number you get free for every one bought)

So for one discount you might store the following:

| discount amount | discount type | buy one get one free |
----------------------------------------------------------
|       10        |   'percent'   |                      |

For another, where BOGOF applies:

| discount amount | discount type | buy one get N free |
----------------------------------------------------------
|                 |               |         1          |

Then it would be up to your PHP to receive these values and act accordingly.