[Solved] What will be the output of this query?SELECT COUNT(DISTINCT category) FROM products; — Ans: Number of unique categories in products | PostgreSQL

PostgreSQL - Aggregate Functions and GROUP BY

What will be the output of this query?

SELECT COUNT(DISTINCT category) FROM products;

ATotal number of rows in products

BNumber of unique categories in products

CSum of all category values

DError because DISTINCT cannot be used inside COUNT

Step-by-Step Solution

Solution:

Step 1: Understand COUNT(DISTINCT)
COUNT(DISTINCT column) counts unique values in that column.
Step 2: Apply to category column
The query returns how many different categories exist in the products table.
Final Answer:
Number of unique categories in products -> Option B
Quick Check:
COUNT(DISTINCT) = count unique values [OK]

Quick Trick: COUNT(DISTINCT) counts unique entries [OK]

Common Mistakes:

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What will be the output of this query?