Database Design for Mere Mortals: A Hands-On Guide to Relational Database Design (3rd Edition) by Michael J. Hernandez

Author:Michael J. Hernandez [Hernandez, Michael J.]
Language: eng
Format: epub, mobi
Publisher: Pearson Education
Published: 2013-02-13T23:00:00+00:00

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Note

I commonly create an ID field (such as EMPLOYEE ID, VENDOR ID, DEPARTMENT ID, CATEGORY ID, and so on) and use it as an artificial candidate key. It always conforms to the Elements of a Candidate Key, makes a great primary key (eventually), and, as you’ll see in Chapter 10, makes the process of establishing table relationships much easier.

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Review the candidate keys you’ve selected and make absolutely certain that they thoroughly comply with the Elements of a Candidate Key. Don’t be surprised if you discover that one of them is not a candidate key after all—incorrectly identifying a field as a candidate key happens occasionally. When this does occur, just remove the “CK” designator from the field name in the table structure. Deleting a candidate key won’t pose a problem so long as the table has more than one candidate key. If you discover, however, that the only candidate key you identified for the table is not a candidate key, you must establish an artificial candidate key for the table. After you’ve defined the new candidate key, remember to mark its name with a “CK” in the table structure.

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