[Solved] Which of the following is true when you use GROUP BY on multiple columns in PostgreSQL? — Ans: Rows are grouped by the combination of values in all specified columns | PostgreSQL

PostgreSQL - Aggregate Functions and GROUP BY

Which of the following is true when you use GROUP BY on multiple columns in PostgreSQL?

ARows are grouped separately by each column independently

BRows are grouped by the first column only

CRows are grouped by the combination of values in all specified columns

DGrouping is ignored if multiple columns are specified

Step-by-Step Solution

Solution:

Step 1: Understand multi-column grouping
When GROUP BY uses multiple columns, it groups rows by the unique combination of values across those columns.
Step 2: Clarify incorrect options
Grouping is not done by only the first column or independently by each column; it is combined. Grouping is never ignored.
Final Answer:
Rows are grouped by the combination of values in all specified columns -> Option C
Quick Check:
GROUP BY multiple columns = group by combined values [OK]

Quick Trick: Multiple columns group by combined values [OK]

Common Mistakes:

Master "Aggregate Functions and GROUP BY" in PostgreSQL

9 interactive learning modes - each teaches the same concept differently

Which of the following is true when you use GROUP BY on multiple columns in PostgreSQL?