KwickClips Databases and SQL · 44 sec · free
How do you get the row count?
Short answer. Multiply the rows of both tables.
What happens to the columns?
They are added together.
Rows multiply
| Table | Rows | Cols |
|---|---|---|
| STUDENT | 1000 | 3 |
| CLUB | 40 | 2 |
| Product | 40000 | 5 |
Remember
| Rows multiply |
| Columns add |
Two small tables. Why is the result so huge? No condition pairs every row with every row. Students have a thousand rows. Clubs have forty. Rows multiply to forty thousand. Columns add to five. Two rules. Rows multiply. Columns add.
This clip is from the full lesson: Working with Two Tables: Cartesian Product, Equi-join and Natural Join — 7 minutes, with the tables, the quick answers and the whole lesson in text.
Useful for: CBSE Class 10 Information Technology (402), CBSE Class 12 Computer Science (083), CBSE Class 12 Informatics Practices (065), CBSE Class 12 Information Technology (802)
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