Multiple choice technology databases

Fill Up: The UNION operator selects only distinct values by default. To allow duplicate values, use __________

  1. UNION ENTIRE

  2. FULL UNION

  3. UNION ALL

  4. none of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

UNION removes duplicate rows by default, combining the result sets and eliminating duplicates. UNION ALL preserves all rows including duplicates from both SELECT statements, which is more efficient when you don't need duplicate elimination. The options 'UNION ENTIRE' and 'FULL UNION' are not valid SQL keywords.

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