in first case it would response and it will show error and 
in second case it will show object belonging to first row 
and column

In First case it will not return any rows. only the colum 
names will be displayed.

In the second case all the records that are available in 
the table will be displayed.

1st Query Output is:

SQL> select * from Emp where null = null;

no rows selected

2nd Query Output is:

All the rows and columns of emp table

select * from Emp where null = null;

null can not be equal to null.So,Condition is not satisfied.
So,it will give only column name.

select * from Emp where 1=1;

1 is always equal to 1.So,Condition is satisfied ,So It 
will give all data which is present in table.

a. select * from Emp where null = null;

null = null will be always false.. so no rows returned..
change the query to "select * from Emp where null is null;"
to select all rows

b. select * from Emp where 1=1;

1 = 1 will be always true.. so all the rows are returned..

a. select * from Emp where null = null;

null= null is always false os no rows returns.

b. select * from Emp where 1=1;

it returns all rows

a)in the first case there is no output only the column 
names alone is displyed

b)in this case all rows will be displayed even for 
1=1,2=2,3=3,..........

Hi,

select * from EMP where null=null;
->null=null is always false so it gives 0 records.
if it is null is null then it fetches all the records in a 
table..

select * from EMP where 1=1;
->it fetches  all the records in a table 
if it is select * from EMP where 1=2;
-->it fetches 0 records..

u can not compare two nulls

null means nothing.so
ANS 1:no row
ANS 2:All row (because of 1=1  is always true for all rows)