juniorSQL
What is GROUP BY?
Updated May 17, 2026
Short answer
GROUP BY groups rows sharing same values.
Deep explanation
It is used with aggregate functions like COUNT, SUM, AVG to summarize data.
Real-world example
Counting employees per department.
Common mistakes
- Selecting non-aggregated columns not in GROUP BY.
Follow-up questions
- Can GROUP BY be used without aggregation?
- What is difference between GROUP BY and DISTINCT?