SQL> --nested loop example
SQL> set serveroutpout on
SP2-0735: unknown SET option beginning "serveroutp..."
SQL> set serveroutput on
SQL> begin
  2    dbms_output.put_line('helloo');
  3    dbms_output.put_line('there!);
  4  end;
  5  /
ERROR:
ORA-01756: quoted string not properly terminated 


SQL> ed
Wrote file afiedt.buf

  1  begin
  2    dbms_output.put_line('helloo');
  3    dbms_output.put_line('there!');
  4* end;
SQL> 
SQL> /
helloo                                                                          
there!                                                                          

PL/SQL procedure successfully completed.

SQL> ed
Wrote file afiedt.buf

  1  begin
  2    dbms_output.put('helloo');
  3    dbms_output.put_line('there!');
  4* end;
SQL> /
helloothere!                                                                    

PL/SQL procedure successfully completed.

SQL> ed
Wrote file afiedt.buf

  1  begin
  2    dbms_output.put('helloo');
  3    dbms_output.put('there!');
  4* end;
SQL> /

PL/SQL procedure successfully completed.

SQL> ed
Wrote file afiedt.buf

  1  begin
  2    dbms_output.put('helloo');
  3    dbms_output.put_line('there!');
  4* end;
  5  /
helloothere!                                                                    

PL/SQL procedure successfully completed.

SQL> ed
Wrote file afiedt.buf

  1  begin
  2    dbms_output.put('helloo');
  3    dbms_output.put('there!');
  4    dbms_output.new_line;
  5* end;
SQL> /
helloothere!                                                                    

PL/SQL procedure successfully completed.

SQL> ed
Wrote file afiedt.buf

  1  begin
  2    dbms_output.put('helloo');
  3    dbms_output.put('there!');
  4    dbms_output.new_line;
  5    dbms_output.put_line('************');
  6* end;
  7  /
helloothere!                                                                    
************                                                                    

PL/SQL procedure successfully completed.

SQL> ed
Wrote file afiedt.buf

  1  begin
  2    dbms_output.put('helloo');
  3    dbms_output.put('there!');
  4    dbms_output.new_line;
  5    dbms_output.put('************');
  6* end;
SQL> /
helloothere!                                                                    

PL/SQL procedure successfully completed.

SQL> --write an anonymous block to print a right angled triangle using *
SQL> --each side will have 4 *s
SQL> begin
  2   for row in 1 ..4
  3     loop
  4       for col in 1 .. row
  5         loop
  6            dbms_output.put('*');
  7          end loop;
  8        dbms_output.new_line;
  9      end loop;
 10  end;
 11  /
*                                                                               
**                                                                              
***                                                                             
****                                                                            

PL/SQL procedure successfully completed.

SQL> spool off