Discussion
A unique, DBMS-supplied identifier used as the primary key of a relation is called a(n):
Answer: D
Correct answer: surrogate key.
A surrogate key is an artificial identifier supplied by the DBMS - an AUTO_INCREMENT column or a sequence value - with no meaning outside the database. It is used as a primary key precisely because it has the properties an ideal key needs: short, numeric, unique and never changing.
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