65
Removing Duplicates
 SELECT  Company.name
 FROM      Company, Product, Purchase
 WHERE   Company.name= Product.maker
              AND  Product.name  = Purchase.product
              AND Purchase.buyer = ‘Joe Blow’
 SELECT DISTINCT Company.name
 FROM      Company, Product, Purchase
 WHERE   Company.name= Product.maker
              AND  Product.name  = Purchase.product
              AND Purchase.buyer = ‘Joe Blow’
¬Multiple copies
¬ Single copies