1. The from class by itself defines a Cartesian product of the relations in the clause.

2. SQL does not have a natural join equivalent. However, natural join can be expressed in terms of a Cartesian product, selection, and projection.

3. For the relational algebra expression

â…¡cname,loan#(borrower ∝ loan)

we can write in SQL,

select distinct cname, borrower.loan#
from borrower, loan
where borrower.loan# = loan.loan#

4. More selections with join: "Find the names and loan numbers of all customers who have a loan at the SFU

branch," we can write in SQL,

select distinct cname, borrower.loan#
from borrower, loan
where borrower.loan# = loan.loan#
and bname="SFU"