The result will be the cartesian product of the rows

Any queries that you run without a where clause would create a cartesian join which has meaningless output.

Though the they haveing common cloumn without mention where or Natural join its will be cartesian product

assume that 2 table are emp dept

now write query like this

select * from emp dept

the out put is emp has 14 records and dept has 4 records

then output is 14x4 56 records you will simply.

Assume you have following two tables:

SQL> select * from aa;
DAT NAME
---- --------

1 Amit
2 Jas

SQL> select * from bb;
DAT ANAME
---- ---------

1 Delhi
3 Mumbai

The following SQL will give me 4 rows
SQL> select * from aa bb;
DAT NAME DAT_1 ANAME
---- ------- ------- ---------

1 Amit 1 Delhi
2 Jas 1 Delhi
1 Amit 3 Mumbai
2 Jas 3 Mumbai

Now if any of the 2 table having 0 rows then the result will : No rows selected. As

in Oracle any addition multiplication division and joining two tables with one as null the output will only be as Null.

To have natural join we need to do following:

SQL> select * from aa natural join bb;
DAT NAME ANAME
--- ------ -------
1 Amit Delhi

I hope this will help.