Cartesian join

A cartesian join - also knwon as cross product - is not very commonly used, at least intentionally. The fact is that it generates an awful huge quantity of data, and usually not with much sense in it.

A cartesian join of a n row table with with a m row table gives an n x m table. Any row in the first table is joined with any row in the second one.

When we really want to get a cartesian join, say we want display all the possible combination between the last names in the contact table with the interest descriptions, we write something like this:

select c.last_name, i.description
from contact c
cross join interest i;