[Solved] What is wrong with this query?SELECT department, SUM(amount) FILTER (WHERE status = 'approved') AS approved_sum, SUM(amount) FILTER (WHERE status = 'rejected') AS rejected_sum FROM transactions; | PostgreSQL

PostgreSQL - Aggregate Functions and GROUP BY

What is wrong with this query?

SELECT department,
       SUM(amount) FILTER (WHERE status = 'approved') AS approved_sum,
       SUM(amount) FILTER (WHERE status = 'rejected') AS rejected_sum
FROM transactions;

AMissing GROUP BY clause for department

BFILTER clause cannot be used with SUM

CIncorrect use of WHERE inside FILTER

DNo error, query is valid

Step-by-Step Solution

Solution:

Step 1: Check GROUP BY usage
The query selects department and aggregates but does not group by department, which is required.
Step 2: Validate FILTER and SUM usage
FILTER with SUM and WHERE is correct syntax, so no error there.
Final Answer:
Missing GROUP BY clause for department -> Option A
Quick Check:
Grouping columns must appear in GROUP BY [OK]

Quick Trick: Use GROUP BY for all non-aggregated selected columns [OK]

Common Mistakes:

Forgetting GROUP BY when selecting non-aggregated columns
Thinking FILTER disallows SUM
Misusing WHERE inside FILTER

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What is wrong with this query?

Step 1: Check GROUP BY usage

Step 2: Validate FILTER and SUM usage

Final Answer:

Quick Check:

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