Question

Consider the following schema:

Distributor (d-id: numeric, d-name: varchar, address: varchar)
Item (i-id: numeric, i-name: varchar, color: varchar)
Inventory (d-id: numeric, i-id: numeric, cost: numeric, instock: numeric)
Where d-id is the distributor's id (primary key in Distributor), i-id is the item's id (primary key in Item), and d-id
together with i-id is the primary key of Inventory. The Inventory relation lists the prices charged for items by
distributors.

Write the following queries using relational algebra:
1. Find the names of distributors who sell some red item.
2. Find the d-ids of distributors who sell some blue or yellow item.
3. Find the d-ids of distributors who sell some blue item or are at 301 Main Street.
4. Find the d-ids of distributors who sell some blue item and some yellow item.
5. Find the d-ids of distributors who sell every item.
6. Find the d-ids of distributors who sell every blue item.
7. Find the d-ids of distributors who sell every blue or yellow item.
8. Find the d-ids of distributors who sell every blue item or sell every yellow item.

Answer 1