[Solved] You wrote this query but it returns fewer rows than expected:SELECT * FROM Products JOIN Categories ON Products.CategoryID = Categories.ID;What is the most likely cause? | SQL

SQL - INNER JOIN

You wrote this query but it returns fewer rows than expected:

SELECT * FROM Products JOIN Categories ON Products.CategoryID = Categories.ID;

What is the most likely cause?

AThere are Products with CategoryID values not present in Categories

BThe query needs a WHERE clause to filter rows

CThe JOIN keyword is missing

DThe join condition column names are swapped

Step-by-Step Solution

Solution:

Step 1: Analyze INNER JOIN behavior
INNER JOIN returns only rows where the join condition matches in both tables.
Step 2: Consider missing matches
If some Products have CategoryID values not in Categories, those Products are excluded, reducing rows.
Final Answer:
There are Products with CategoryID values not present in Categories -> Option A
Quick Check:
Missing matches cause fewer rows in INNER JOIN [OK]

Quick Trick: INNER JOIN excludes rows without matching keys [OK]

Common Mistakes:

MISTAKES

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