KwickClips Databases and SQL · 36 sec · free
What does GROUP BY do first?
Short answer. It puts rows with the same value together.
When does the aggregate run?
After the groups are formed.
Group, then aggregate
| sec | Marks | COUNT(*) |
|---|---|---|
| A | 88, 65, 91 | 3 |
| B | 72, NULL | 2 |
Remember
| Group first |
| Then aggregate each group |
Avg gives one answer. How do you get one per section? First, rows with the same section form a group. Then count runs on each group separately. Group first. Then aggregate each group.
This clip is from the full lesson: GROUP BY and HAVING — 6 minutes, with the tables, the quick answers and the whole lesson in text.
Useful for: CBSE Class 12 Computer Science (083), CBSE Class 12 Informatics Practices (065), CBSE Class 12 Information Technology (802)
More KwickClips from this lesson
How many rows does GROUP BY return?36 sec
Where do aggregates belong?36 sec
How many rows remain after HAVING COUNT(*) › 1?36 secDisclaimer. KwickAcademy is free study material for general learning and revision. Parts of it, including the voice-over, are produced with the help of AI tools and may contain errors; if you spot one, please tell us and we will correct it. Syllabus, marks and exam details follow the latest official board publications available to us, and boards can change them at any time, so always confirm against your board's official website and your school. Using this material does not guarantee any marks or result. Board names and trademarks belong to their owners; Kwickprep is not affiliated with or endorsed by any examination board. We never ask for passwords, OTPs or ID numbers. Your progress is saved only in this browser. Full disclaimer · Privacy