[Solved] Identify the error in this query:SELECT product_id, region, COUNT(*) FROM sales GROUP BY product_id; | PostgreSQL

PostgreSQL - Aggregate Functions and GROUP BY

Identify the error in this query:

SELECT product_id, region, COUNT(*) FROM sales GROUP BY product_id;

ACOUNT(*) cannot be used with GROUP BY.

BMissing region in GROUP BY causes error.

Cproduct_id cannot be grouped alone.

DSyntax error due to missing FROM clause.

Step-by-Step Solution

Solution:

Step 1: Check SELECT columns vs GROUP BY columns
SELECT includes product_id and region, but GROUP BY only has product_id.
Step 2: Understand PostgreSQL grouping rules
All non-aggregated columns in SELECT must appear in GROUP BY; region is missing.
Final Answer:
Missing region in GROUP BY causes error. -> Option B
Quick Check:
All SELECT non-aggregates must be in GROUP BY [OK]

Quick Trick: Include all non-aggregated SELECT columns in GROUP BY [OK]

Common Mistakes:

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Identify the error in this query: