[Solved] What is wrong with this query?SELECT id, salary, SUM(salary) OVER (PARTITION BY department ORDER BY salary) AS running_total FROM employees; | PostgreSQL

PostgreSQL - Window Functions in PostgreSQL

What is wrong with this query?
SELECT id, salary, SUM(salary) OVER (PARTITION BY department ORDER BY salary) AS running_total FROM employees;

AQuery is correct and will return running totals per department

BORDER BY cannot be used inside SUM() OVER with PARTITION BY

CSUM() cannot be used as a window function

DMissing window frame clause causes running_total to be cumulative sum of all rows in partition

Step-by-Step Solution

Solution:

Step 1: Understand default window frame behavior
Without explicit frame, SUM() OVER with ORDER BY uses RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW, but RANGE with ORDER BY on salary may behave unexpectedly.
Step 2: Effect of missing frame clause
It may sum all rows with same salary value, not strictly cumulative by row; explicit ROWS frame is safer for running totals.
Final Answer:
Missing window frame clause causes running_total to be cumulative sum of all rows in partition -> Option D
Quick Check:
Specify ROWS frame for precise running totals [OK]

Quick Trick: Use ROWS frame for exact running totals, not default RANGE [OK]

Common Mistakes:

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What is wrong with this query?