A join that included more than one table using keyword CROSS is called cross join.
The output of a such type of join is called Cartesian product.
In cross join each row of first table is joined to with the each row of second table.
The number of rows in the result set is the multiple of the first table rows and second table rows.
SELECT column_name 1, column_name 2....column_name n FROM table_name CROSS JOIN table_name
SELECT * FROM sales CROSS JOIN publishers
returns 168 rows, after cross join 21 rows of sales table and 8 rows of publishers tables.