Question

Please, No handwriting COURSE;
introduction to database
thank you for your efforts and time
The following set of schemas is given:

Customer (name, age, gender)
Visit (name, store)
Receipt (name, product)
Offer (store, product, price)

Write the following queries in relational algebra, using the above schema:
1. Find all stores visited by at least one customer under the age of 18.
2. Find the names of all females who bought either product # 1 or product #2.
3. Find all stores that offer at least one product that the customer Ahmed bought for less than 10 Riyal.
4. Find the names of customers who bought product # 1 or product # 2. [
5. Find the names of customers who bought product # 3 or are over the age of 18.

Answer 1

1.answer)

Π_store(σ_{customer.name=Visit.name ^ age<18}(Customer x Visit))

2.answer)

Π_{Customer.name}(σ_{customer.name=Receipt.name ^ gender="female" ^(product=1 v product=2)}(Customer x Receipt))

3.answer)

Π_Offer.store(σ_{customer.name=Receipt.name^customer.name="Ahmed"^Receipt.product=Offer.product ^ price<10)}(Customer x Receipt xOffer))

4.answer)

Π_{Customer.name}(σ_{customer.name=Receipt.name ^(product=1 v product=2)}(Customer x Receipt))

5.answer)

Π_{Customer.name}(σ_{customer.name=Receipt.name ^(product=3 v age>18)}(Customer x Receipt))