3
Null Values and Outerjoins
•Explicit joins in SQL:
• Product(name, category)
•      Purchase(prodName, store)
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•Same as:
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•But Products that never sold will be lost !
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SELECT Product.name, Purchase.store
FROM     Product JOIN Purchase ON
                              Product.name = Purchase.prodName
SELECT Product.name, Purchase.store
FROM     Product, Purchase
WHERE   Product.name = Purchase.prodName