[Solved] Identify the error in this query:SELECT department, AVG(salary) FROM employees GROUP BY role; — Ans: Grouping column does not match selected non-aggregated column | PostgreSQL

PostgreSQL - Aggregate Functions and GROUP BY

Identify the error in this query:

SELECT department, AVG(salary) FROM employees GROUP BY role;

AGrouping column does not match selected non-aggregated column

BAVG() cannot be used with GROUP BY

CMissing WHERE clause for filtering

DGROUP BY must include all columns in the table

Step-by-Step Solution

Solution:

Step 1: Check selected columns vs GROUP BY
Selected non-aggregated column is department, but grouping is by role, causing mismatch.
Step 2: Understand GROUP BY rules
All selected columns that are not aggregated must appear in GROUP BY clause.
Final Answer:
Grouping column does not match selected non-aggregated column -> Option A
Quick Check:
GROUP BY columns must match non-aggregated SELECT columns [OK]

Quick Trick: Non-aggregated SELECT columns must be in GROUP BY [OK]

Common Mistakes:

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Identify the error in this query: