Multiple choice technology databases

Which of the following is used to indicate a column will not accept NULL values and can be referenced in another table's foreign key specification?

  1. Check constraint

  2. Default constraint

  3. Unique constraint

  4. Informational constraint
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C Correct answer
Explanation

A Unique constraint ensures all values in a column are distinct and allows the column to be referenced by a foreign key. While Unique constraints allow NULLs by default, when combined with NOT NULL (implied by 'will not accept NULL'), it creates a key suitable for foreign key references. Check constraints validate values, Default constraints set initial values, and Informational constraints are for documentation only.

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