# Relational Schema

Question 3 (30 marks)
(a) (18 marks) Consider the relational schema R(A, B, C, D, E, G, H, I, J) and a set of
functional dependencies F = {BD → CH, BC → HI, EI → H, H → AB, I →
E, EJ → I}. Note that A, B, C, D, E, G, H, I, J are attributes.
• Find a minimal cover Fm for F. (3 marks)
• Compute all the candidate keys of R with respect to F. (4 marks)
• Regarding F, is the decomposition R1 = {ABCDH}, R2 = {EGHIJ} of R
• Determine the highest normal form of R. If R is not in the BCNF, decompose
R into BCNF and indicate a key in each of the result tables by underlining the
attributes.(6 marks)
(b) (12 marks) Consider the following relational schema for a restaurant-review website:
• Customer(cID, name, age, gender, email),
• Restaurant(rID, location),
• Review(rID, cID, content)
Below are detailed descriptions for the fields in each schema:
• Customer: For each customer, we record cID, name, age, gender and email.
cID is the primary key.
• Restaurant: For each restaurant, we record rID and its location. rID is the
primary key.
• Review: For each review, we record the rID of restaurant, the cID of customer,
and the content of the review. The combination of rID and cID is the primary
key.
Use relational algebra to answer the following questions:
1. List the rID of restaurants that are only reviewed by male customers or only
reviewed by female customers. (4 marks)
2. List the cID of customers who have reviewed all the restaurants or never review
any restaurant. (4 marks)
3. List the average age of the customers of each gender who have reviewed at least
one restaurant. (4 marks)

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