I made a promo code function, the member in the purchase of a certain item, how to give this coupon code to the member

I made a promo code function, the member in the purchase of a certain item, how to give this coupon code to the member
I got a promo code generation function in the mall backstage, how do I go to specify this coupon code when adding a product, (note: A number of different coupon code, the same denomination), and then the member in the front desk to buy this product, how to release the coupon code, this I think half a day did not understand
------to solve the idea----------------------
When adding a product, randomly generate several coupon codes (several can be self-determined), and stored in the database, and the product to correspond well
At the front desk to give a button or something, the user click on the product ID to find a coupon code to the user
The coupon code must have the Status field, identify this coupon code is not received, has been picked, not used, has been used .... It depends on your own logic.
------to solve the idea----------------------
Isn't there a promo code table?
Bind the membership ID on it.

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