SQL & PL/SQL

Hi
i'm having a sql script in that there are three queries.

i want to exit from the sql script displaying as "No duplicates" if i have no records for the first query, can anyone suggest me how to do it in a sql script, without anonymous block, below i have given my script

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whenever sqlerror exit sql.sqlcode
set serveroutput on
column fn new_value filename
select 'remove_duplicates_'||to_char(sysdate, 'yyyymmddhh24miss')||'.log' as fn from dual;
spool E:/&filename

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prompt 'Checking for duplicates'
---------------------------------------
select account_id, count(1)
from accounts
group by account_id
having count(1) > 1;

---------------------------------------
prompt 'Records to be deleted'
---------------------------------------

select *
from accounts
where decode ( substr(account_id,1,3),'COG',1,0)=1
group by account_id
having count(1) > 1;

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prompt ' Deleting duplicates'
---------------------------------------

delete
from accounts
where account_id in (
select account_id
from accounts
where decode ( substr(account_id,1,3),'COG',1,0)=1
group by account_id
having count(1) > 1
);

commit;
/