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07-20-2023, 02:48 PM
A **super key** of an entity set is a set of one or more attributes whose values uniquely determine each entity.
A **candidate key** of an entity set is a minimal *super key*.
Let's go on with customer, loan and borrower sets that you can find an image from the link ≥≥ [1]
- Rectangles represent entity sets ≥≥ [1]
- Diamonds represent relationship set ≥≥ [1]
- Elipses represent attributes ≥≥ [1]
- Underline indicates Primary Keys ≥≥ [1]
*customer_id* is the **candidate key** of the customer set, *loan_number* is the **candidate key** of the loan set.
Although several candidate keys may exist, one of the candidate keys is selected to be the primary key.
Borrower set is formed *customer_id* and *loan_number* as a relationship set.
[1]:
A **candidate key** of an entity set is a minimal *super key*.
Let's go on with customer, loan and borrower sets that you can find an image from the link ≥≥ [1]
- Rectangles represent entity sets ≥≥ [1]
- Diamonds represent relationship set ≥≥ [1]
- Elipses represent attributes ≥≥ [1]
- Underline indicates Primary Keys ≥≥ [1]
*customer_id* is the **candidate key** of the customer set, *loan_number* is the **candidate key** of the loan set.
Although several candidate keys may exist, one of the candidate keys is selected to be the primary key.
Borrower set is formed *customer_id* and *loan_number* as a relationship set.
[1]:
