Cartesian Product in SQL

Cartesian Products: If two tables in a join query have no join condition, Oracle returns their Cartesian product. Oracle combines each row of one table with each row of the other. A Cartesian product always generates many rows and is rarely useful.• A Cartesian product is formed when:– A join condition is omitted– A join condition is invalid– All rows in the first table are joined to all rows in the second table

• To avoid a Cartesian product, always include a valid join condition in a WHERE clause.

Example-

we have two table emp and dept in scott user
emp have 14 rows and dept have 5 rows
if we write this query
select emp.ename,emp.sal,dept.dname from emp,dept;
this query provide you 70 rows
this called cartesian product 14*5