[Solved] Consider these tables:products(id, name, price)sales(id, product_id, quantity)What is the problem with this query?SELECT * FROM products NATURAL JOIN sales; | PostgreSQL

PostgreSQL - Joins in PostgreSQL

Consider these tables:
products(id, name, price)
sales(id, product_id, quantity)
What is the problem with this query?

SELECT * FROM products NATURAL JOIN sales;

AIt will return all rows without filtering.

BIt will cause a syntax error because NATURAL JOIN requires USING clause.

CIt will join on <code>id</code> columns, which are different keys, causing incorrect results.

DIt will join correctly on <code>product_id</code> automatically.

Step-by-Step Solution

Solution:

Step 1: Identify common columns
Both tables have a column named id, but they represent different things.
Step 2: Understand NATURAL JOIN risk
NATURAL JOIN joins on all same-named columns, so it joins on id which mismatches keys, causing wrong results.
Final Answer:
It will join on id columns, which are different keys, causing incorrect results. -> Option C
Quick Check:
Unintended column match = wrong join [OK]

Quick Trick: Check if same-named columns mean same data before NATURAL JOIN [OK]

Common Mistakes:

Master "Joins in PostgreSQL" in PostgreSQL

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Consider these tables: