[Solved] A query using NATURAL JOIN returns fewer rows than expected. What is a common cause? — Ans: The join matches on all common columns, filtering out rows where any common... | PostgreSQL

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:

Step 1: Recall NATURAL JOIN filtering
NATURAL JOIN returns rows where all common columns match exactly.
Step 2: Understand why fewer rows appear
If any common column values differ, those rows are excluded, reducing the result set.
Final Answer:
The join matches on all common columns, filtering out rows where any common column differs. -> Option A
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:

Master "Joins in PostgreSQL" in PostgreSQL

9 interactive learning modes - each teaches the same concept differently

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