Multiple choice

The constraint used to avoid keying in repeated values into a column must be declared_____________.

  1. UNIQUE

  2. DISTINCT

  3. CHECK

  4. None of these
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A Correct answer
Explanation

The UNIQUE constraint ensures that all values in a column are different - no two rows can have the same value for that column. DISTINCT is used in SELECT queries to remove duplicates from results, CHECK validates values against a condition, and these are not the correct constraint for preventing repeated values.

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