Multiple choice

Which of the following operators is used in a correlated subquery?

  1. IN

  2. EXISTS

  3. UNION

  4. INTERSECT
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B Correct answer
Explanation

The EXISTS operator is specifically designed for correlated subqueries, testing whether the subquery returns any rows. It's evaluated for each row of the outer query. While IN can also be used in subqueries, EXISTS is the canonical operator for correlated subqueries because it can stop processing once a match is found. UNION and INTERSECT are set operators for combining queries, not subquery correlation.

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