Use of Cartesian Product in SQL

 Cartesian product returns a number of rows  from 1st * 2nd  Table. 
if the first table has 20 rows and the second table has 3 rows, then  result will be 20 * 3 = 60 rows. Cartesian Product is also well known as Cross Join.  We write a syntax as below--

SELECT * FROM Tbllecture

CROSS JOIN Tblteacher

The Cartesian product returns a number of rows equal to the product of all rows in all the tables being joined.
example
if the first table has 10 rows and the second table has 5 rows, the result will be 10 * 5 = 50 rows.

it also known as cross join

Please refer

http://msdn.microsoft.com/en-us/library/ms190690%28v=sql.105%29.aspx