Bird
0
0

A query using NATURAL JOIN returns fewer rows than expected. What is a common cause?

medium📝 Debug Q7 of 15
PostgreSQL - Joins in PostgreSQL
A query using NATURAL JOIN returns fewer rows than expected. What is a common cause?
AThe join matches on all common columns, filtering out rows where any common column differs.
BNATURAL JOIN always returns all rows from both tables.
CThe query syntax is incorrect.
DThe tables have no common columns.
Step-by-Step Solution
Solution:
  1. Step 1: Recall NATURAL JOIN filtering

    NATURAL JOIN returns rows where all common columns match exactly.
  2. Step 2: Understand why fewer rows appear

    If any common column values differ, those rows are excluded, reducing the result set.
  3. Final Answer:

    The join matches on all common columns, filtering out rows where any common column differs. -> Option A
  4. Quick Check:

    Fewer rows = strict matching on all common columns [OK]
Quick Trick: NATURAL JOIN filters rows on all common columns matching [OK]
Common Mistakes:
  • Assuming NATURAL JOIN returns all rows
  • Blaming syntax errors for fewer rows
  • Ignoring filtering effect of multiple join columns

Want More Practice?

15+ quiz questions · All difficulty levels · Free

Free Signup - Practice All Questions
More PostgreSQL Quizzes