The from Clause

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

   

   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''