Multiple choice technology databases

Can Composite Key be Null?

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A composite key combines multiple columns to create a unique identifier. The entire combination cannot be NULL, though individual components might allow NULLs in some systems. For the key to function as an identifier, at least one component must be non-NULL.

AI explanation

False is correct — a composite key cannot be null (in whole or, under standard primary-key rules, in any of its constituent columns). A primary key, whether single-column or composite, must satisfy the NOT NULL and uniqueness constraints for every part of the key, since a null component would make it impossible to guarantee uniqueness or use it reliably for referential integrity. This is why 'Can Composite Key be Null?' correctly resolves to False.

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