instance of content of database Key A key is a subset of attributes that uniquely identify a row subset (c shape with line under it) of attributes, usually defined by people, should be minimal, Ensure no other can be a subset, For instance, customer name is minimal so it’s a candidate key, One candidate key is selected to be a primary key – Defined over a single relation, unique way of identifying a record in a relation, subset of attributes that can uniquely define a record, usually defined by people…
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