Keys K is a superkey of R if values for K are sufficient to identify a unique tuple of each possible relation r(R) by"possible rwe mean a relation r that could exist in the enterprise we are modeling. Example: Icustomer-name, customer-street and Icustomer-name] are both superkeys of Customer, if no two customers can possibly have the same name K is a candidate key if K is minimal Example: Icustomer-name] is a candidate key for Customer, since it is a superkey(assuming no two customers can possibly have the same name), and no subset of it is a superkey Database System Concepts 3.12 OSilberschatz, Korth and SudarshanDatabase System Concepts 3.12 ©Silberschatz, Korth and Sudarshan Keys K is a superkey of R if values for K are sufficient to identify a unique tuple of each possible relation r(R) by “possible r” we mean a relation r that could exist in the enterprise we are modeling. Example: {customer-name, customer-street} and {customer-name} are both superkeys of Customer, if no two customers can possibly have the same name. K is a candidate key if K is minimal Example: {customer-name} is a candidate key for Customer, since it is a superkey (assuming no two customers can possibly have the same name), and no subset of it is a superkey