SQL CROSS JOIN
A CROSS JOIN returns every possible combination of rows from two tables.
It’s called a Cartesian product – no ON clause is required.
🔹 Basic Syntax
SELECT *
FROM table1
CROSS JOIN table2;🔹 Example: All Product and Region Combinations
SELECT
p.product_name,
r.region_name
FROM products p
CROSS JOIN regions r;✅ If there are 5 products and 3 regions, you get 5 × 3 = 15 rows – every combination.
🔹 Use Cases
- Generate all combinations (e.g., size × color)
- Testing and simulations
- Matrix-style reports
⚠️ Caution
CROSS JOIN can return very large results if the tables are big. Use it carefully.
🧠 Quick Recap
| Key Point | Explanation |
|---|---|
CROSS JOIN | Returns all combinations of rows from both tables |
| Output size | Multiplies row counts (rows_A × rows_B) |
No ON clause | Doesn’t need a join condition |
| Use cases | All pairings, simulations, exhaustive comparisons |
💡 Use CROSS JOIN when you need every combination of two sets