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Which set operation returns only the rows common to both SELECT queries?

easy📝 Conceptual Q2 of 15
PostgreSQL - Set Operations and Advanced Queries
Which set operation returns only the rows common to both SELECT queries?
AUNION
BINTERSECT
CEXCEPT
DJOIN
Step-by-Step Solution
Solution:

  1. Step 1: Identify INTERSECT behavior

    INTERSECT returns only rows that appear in both SELECT query results.

  2. Step 2: Compare with other operations

    UNION combines all unique rows; EXCEPT returns rows in first query but not second; JOIN combines rows based on matching columns.

  3. Final Answer:

    INTERSECT returns only common rows -> Option B

  4. Quick Check:

    INTERSECT = Common rows only [OK]
Quick Trick: INTERSECT finds common rows between queries [OK]
Common Mistakes:
  • Confusing INTERSECT with UNION
  • Thinking JOIN is a set operation
  • Assuming EXCEPT returns common rows

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