SQL & PL/SQL

Hi
I have a table emp as the following:-

SQL> desc emp
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------

 EMPLOYEE_ID                                        NUMBER(6)
 
 SALARY                                             NUMBER(8,2)
 
 STARS                                              VARCHAR2(50)

I want to create a PL/SQL block that inserts an asterisk in the stars coulmn for every
employee's salary that more than $1,000 .
So I have written this code

SQL> declare
  2  sal emp.salary%type;
  3  begin
  4  while sal > 1000 loop
  5  insert into emp(stars) values('*');
  6  end loop;
  7  end ;
  8  /

PL/SQL procedure successfully completed.

But no asterisk entered
SQL> select * from emp where stars is not null;

no rows selected
Any help please.