MySQL SQLLesson 32Free preview

MySQL CROSS JOIN

This lesson is part of MySQL · All levels

Summary

CROSS JOIN returns the result of the cross multiplication: each row of the left table is paired with all the rows of the right table. If the left table has 3 rows and the right table has 4 rows, it's 12 rows. Cross JOIN does not require an ON condition, and in practice is often used to create data combinations such as product color sizes lists or scenario simulations.

Key points

CROSS JOIN results in the Cartesian product of two tables
The number of rows resulting = the number of rows of the left table × the number of rows of the right table
No need for an ON clause because all combinations are constants
When using WHERE, the result is effectively equal to INNER JOIN.

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