1
$\begingroup$

Assuming I have two relations:

Supplier [ID (PK), Name, City, Country] and

Item [ID (PK), Name, Department, Price, Stock, Supplier_ID (FK)]

What would be the easiest way to determine the following statement both in domain and tuple relational calculus: "List the IDs and names of those suppliers, who have delivered at least three different items"?

If, for example, I had to find out if a supplier had delivered only items at a certain price range or if an item was sitting in this or that department, that would't be difficult. It's the "at least three different items" part I can't quite figure out yet. I'm assuming I'd have to juggle around tuples with several different item IDs through AND/OR operators, with some item IDs not equal to other item IDs etc.

Any help with my task would be greatly appreciated!

Improve this question
$\endgroup$
2
  • $\begingroup$ I think this can be achieved using existential quantifiers. I am rusty on TRC so leaving this as a comment $\left \{s\mid s\in Supplier \land \exists\, i \in Item(s[id]=i[supplier\_id]\,\land \exists i1,i2,i3 \land i1[id]\neq i2[id] \land i2[id]\neq i3[id] \land i1[id]\neq i3[id]) \land i1[s[id]]=i2[s[id]] \land i2[s[id]]=i3[s[id]] \right \}$ $\endgroup$
    – Rinkesh P
    Nov 29, 2022 at 7:36
  • $\begingroup$ @RinkeshP Thank you, friend. Exactly what I needed! Just wasn't quite sure how to equate or negate those item IDs. Cheers! $\endgroup$
    – T.E.
    Nov 29, 2022 at 9:51

0

Reset to default

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.