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Is primary key mandatory?

royjayd asked
Last Modified: 2012-08-14
hi guys
I have a table 'supplier' with these 4 columns

supplier_id   product_id  supplier_name   cost
1                      100                   IIT                        $200
2                      100                   RAM                   $199
2                      200                  RAM                   $500
3                      500                   GAC                   $1499

I have multiple suppliers selling products but 2 different suppliers
can sell the same product,  example i have supplier_id 1 and
supplier_id 2 selling the product with product_id 100 (for a different cost)

so in this scenario what could be my primary key and what should be the
foreign key?

Do i relly need a primary key in the first place? or can i just use composite keys in this scenario?

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