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 secVoice-over is AI-generated; the script is written and checked by Kajal Ma'am. Confirm anything you plan around against your official board document. We never ask for a password or an OTP.