How can you combine GROUPING SETS with ROLLUP to get totals by department, and by department-month with subtotals for department and grand total?

hard📝 Application Q9 of 15

PostgreSQL - Aggregate Functions and GROUP BY

How can you combine GROUPING SETS with ROLLUP to get totals by department, and by department-month with subtotals for department and grand total?

AUse GROUP BY CUBE(department, month)

BUse GROUP BY ROLLUP(department, month) only

CUse GROUPING SETS ((department), (month)) only

DUse GROUPING SETS ((department, month), (department), ()), combining ROLLUP and GROUPING SETS

Step-by-Step Solution

Solution:

Step 1: Understand the requirement
We want totals by department-month, by department, and grand total (empty grouping).
Step 2: Use GROUPING SETS with empty set for grand total
GROUPING SETS ((department, month), (department), ()) includes all needed groupings and grand total.
Final Answer:
Use GROUPING SETS ((department, month), (department), ()), combining ROLLUP and GROUPING SETS -> Option D
Quick Check:
Empty parentheses in GROUPING SETS give grand total [OK]

Quick Trick: Empty set () in GROUPING SETS gives grand total [OK]

Common Mistakes:

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