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Subqueries & CTEs interview questions

18 real Subqueries & CTEs questions from the SQL bank, as asked in Indian campus drives and tech interviews. Every question has a verified answer and an AI-tutor explanation on placd — free to start.

1. What is Subquery?

Mid
  1. A.a WITH-clause named temporary result set that improves readability and enables recursion
  2. B.tests whether a subquery returns any rows, short-circuiting on the first match
  3. C.a CTE that references itself to traverse hierarchies such as an org chart
  4. D.a query nested inside another, used in SELECT, FROM, or WHERE
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3. Which statement is correct?

Mid
  1. A.Subquery — a subquery that references the outer query and is re-evaluated for each outer row
  2. B.Subquery — tests whether a subquery returns any rows, short-circuiting on the first match
  3. C.Subquery — a CTE that references itself to traverse hierarchies such as an org chart
  4. D.Subquery — a query nested inside another, used in SELECT, FROM, or WHERE
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4. What is Correlated subquery?

Senior
  1. A.a CTE that references itself to traverse hierarchies such as an org chart
  2. B.a WITH-clause named temporary result set that improves readability and enables recursion
  3. C.tests whether a subquery returns any rows, short-circuiting on the first match
  4. D.a subquery that references the outer query and is re-evaluated for each outer row
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6. Which statement is correct?

Senior
  1. A.Correlated subquery — a query nested inside another, used in SELECT, FROM, or WHERE
  2. B.Correlated subquery — a subquery that references the outer query and is re-evaluated for each outer row
  3. C.Correlated subquery — a WITH-clause named temporary result set that improves readability and enables recursion
  4. D.Correlated subquery — tests whether a subquery returns any rows, short-circuiting on the first match
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7. What is CTE?

Mid
  1. A.a query nested inside another, used in SELECT, FROM, or WHERE
  2. B.a WITH-clause named temporary result set that improves readability and enables recursion
  3. C.a subquery that references the outer query and is re-evaluated for each outer row
  4. D.IN compares against a value list; EXISTS checks row existence and is often faster for large subqueries
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9. Which statement is correct?

Mid
  1. A.CTE — tests whether a subquery returns any rows, short-circuiting on the first match
  2. B.CTE — IN compares against a value list; EXISTS checks row existence and is often faster for large subqueries
  3. C.CTE — a WITH-clause named temporary result set that improves readability and enables recursion
  4. D.CTE — a subquery that references the outer query and is re-evaluated for each outer row
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10. What is Recursive CTE?

Senior
  1. A.a subquery that references the outer query and is re-evaluated for each outer row
  2. B.a WITH-clause named temporary result set that improves readability and enables recursion
  3. C.IN compares against a value list; EXISTS checks row existence and is often faster for large subqueries
  4. D.a CTE that references itself to traverse hierarchies such as an org chart
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12. Which statement is correct?

Senior
  1. A.Recursive CTE — a subquery that references the outer query and is re-evaluated for each outer row
  2. B.Recursive CTE — a CTE that references itself to traverse hierarchies such as an org chart
  3. C.Recursive CTE — a query nested inside another, used in SELECT, FROM, or WHERE
  4. D.Recursive CTE — a WITH-clause named temporary result set that improves readability and enables recursion
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13. What is EXISTS?

Mid
  1. A.IN compares against a value list; EXISTS checks row existence and is often faster for large subqueries
  2. B.a WITH-clause named temporary result set that improves readability and enables recursion
  3. C.tests whether a subquery returns any rows, short-circuiting on the first match
  4. D.a subquery that references the outer query and is re-evaluated for each outer row
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15. Which statement is correct?

Mid
  1. A.EXISTS — tests whether a subquery returns any rows, short-circuiting on the first match
  2. B.EXISTS — a query nested inside another, used in SELECT, FROM, or WHERE
  3. C.EXISTS — IN compares against a value list; EXISTS checks row existence and is often faster for large subqueries
  4. D.EXISTS — a WITH-clause named temporary result set that improves readability and enables recursion
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16. What is IN vs EXISTS?

Senior
  1. A.tests whether a subquery returns any rows, short-circuiting on the first match
  2. B.a subquery that references the outer query and is re-evaluated for each outer row
  3. C.IN compares against a value list; EXISTS checks row existence and is often faster for large subqueries
  4. D.a WITH-clause named temporary result set that improves readability and enables recursion
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18. Which statement is correct?

Senior
  1. A.IN vs EXISTS — a subquery that references the outer query and is re-evaluated for each outer row
  2. B.IN vs EXISTS — IN compares against a value list; EXISTS checks row existence and is often faster for large subqueries
  3. C.IN vs EXISTS — tests whether a subquery returns any rows, short-circuiting on the first match
  4. D.IN vs EXISTS — a WITH-clause named temporary result set that improves readability and enables recursion
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