Question 1

The relational schema shown below is part of an inter-library loan system. Borrowers can borrow books from different libraries.

a) Express the following queries in Relational Algebra:

i. Produce a relation that shows the borrower surname, borrower number and book titles for all borrowers at the Hatton Cross branch.

ii. Produce a relation that shows the following information: borrower surname, borrower number for all borrowers that borrowed books from public libraries which have holdings above 30,000.

b) Derive the result for the following relational algebra queries:

i. ΠLibrary Branch (σHoldings <=50000 ˄District= “South London” (Library)))

ii. ΠLibrary Branch (σDistrict ≠ ‘Berkshire’ ˄ Holdings >= 100000(Library))

iii. ΠBorrower surname (σBook_Title = “Coral Bridge” (Loan_Record))

c) Give a definition of query optimisation and outline how relational algebra can be used in the process of query optimisation..

d) Give an outline of the main features of Relational Calculus.