p is ref cursor;
 p1 p;
 if :P_1 is null then
   open p1 for select * from emp;
 else if :p_1=7369
   open p1 for select * from emp where empno=7369;
 else
   open p1 for select * from emp where deptno=10;
end if;

 The above code is working depending 
upon parameters in run time.

I am asking about, i can able to do 
the above codes by lexical parameter also.

in my data model i am using select * from emp &p

p is lexical parameter, i can able 
to give a parameter at 
run time like this

 where empno=7369
 where deptno=10