[Solved] Consider the table sales with columns region, product, and amount. What will the following query return?SELECT region, product, SUM(amount) FROM sales GROUP BY ROLLUP(region, product); | PostgreSQL

PostgreSQL - Aggregate Functions and GROUP BY

Consider the table sales with columns region, product, and amount. What will the following query return?

SELECT region, product, SUM(amount) FROM sales GROUP BY ROLLUP(region, product);

ASum of amounts grouped only by product

BSum of amounts without any grouping

CSum of amounts grouped by region with no subtotals

DSum of amounts grouped by region and product, plus subtotals by region and a grand total

Step-by-Step Solution

Solution:

Step 1: Understand ROLLUP with two columns
ROLLUP(region, product) groups by (region, product), then by region only, then grand total.
Step 2: Analyze query result
The query returns sums for each region-product pair, subtotals per region, and a grand total row.
Final Answer:
Sum of amounts grouped by region and product, plus subtotals by region and a grand total -> Option D
Quick Check:
ROLLUP(region, product) = detailed + subtotals + total [OK]

Quick Trick: ROLLUP adds subtotals from right to left grouping [OK]

Common Mistakes:

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Consider the table sales with columns region, product, and amount. What will the following query return?