Comments

• • Jon Dron@jond

  

  Jon Dron November 13, 2018 - 7:31pm

  This is looking good, Liliana. I wonder, though, whether there is another entity lurking in the relationship between an employee and a cash register? Seems to me that a cash register will be used by many employees, and an employee may use many cash registers, which implies to me that there must be an associative entity between them. I've never worked as a sales clerk in a supermarket so am not sure of the terminology but I've noticed the ones doing so talking about 'shifts' on the till: might be a possible entity? Don't forget to draw relationships explicitly, wherever there's a foreign key: there's one between receipt and customer_more_reward, for instance (the foreign key implies that the many end is at the receipt, I think). My own experience of the More Rewards program suggests that the phone number is very important to the system and *might* be a significant index. It also suggests that redemption matters (not in the religious sense!) - quite a lot of products are offered at a reduced price or even free with More Rewards, and that makes a difference on the receipt (and to the customer's reward points - might there be a need to record these?). Beware, too, of complexities around those offers. Some of them are affected by the number of items purchased. This may imply further entities - perhaps including a 'discount' entity that affects a receipt? It would not be a bad idea to look at a real receipt to make sure that you've picked up on all the possible attributes, including those that are implied. Another useful intuition pump might be to think about whether and how the model changes for online customers getting their groceries delivered.