Multiple choice technology programming languages

Which constraint can be defines only at the column level?

  1. UNIQUE

  2. NOT NULL

  3. CHECK

  4. PRIMARY KEY

  5. FOREIGN KEY
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B Correct answer
Explanation

NOT NULL is strictly a column-level constraint that prevents null values in a specific column and cannot be defined at the table level. UNIQUE, CHECK, PRIMARY KEY, and FOREIGN KEY can all be defined at either column level (for single columns) or table level (for multiple columns or composite constraints).

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