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Alternate key

 
Sci-Tech Dictionary: alternate key
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(′öl·tər·nət ′kē)

(computer science) A key on a computer keyboard that does not itself generate a character but changes the nature of the character generated by another key when depressed simultaneously with it; similar to the control and shift keys. Abbreviated ALT key.

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Wikipedia: Alternate key
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You may have meant the Alt key on the keyboard.

In the context of relational databases, an alternate key (or secondary key) is any candidate key which is not selected to be the primary key (PK).

For example, a relational database with a table "employee" could have attributes like "employee_id", "national_insurance_number", and so on. In this case, both "employee_id" and "national_insurance_number" serve as unique identifiers for a given employee, and could thus arguably be used for a primary key. Hence, both of them are called "candidate keys". If, for example, "national_insurance_number" was chosen as the primary key, "employee_id" would become the alternate key.



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Sci-Tech Dictionary. McGraw-Hill Dictionary of Scientific and Technical Terms. Copyright © 2003, 1994, 1989, 1984, 1978, 1976, 1974 by McGraw-Hill Companies, Inc. All rights reserved.  Read more
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