create table  order_dtls( cutomer_id number(10), order_id(7));

insert into order_dtls values(1234567,1); 
insert into order_dtls values(1234567,2); 
insert into order_dtls values(1234567,3); 
insert into order_dtls values(1234567,4); 
insert into order_dtls values(1234567,5); 
insert into order_dtls values(1234461,1); 
insert into order_dtls values(1234461,2); 
insert into order_dtls values(1234461,3); 
insert into order_dtls values(1234761 ,1); 
insert into order_dtls values(1234761 ,2); 
insert into order_dtls values(1234761 ,3); 
insert into order_dtls values(1234761 ,4); 
insert into order_dtls values(1234761 ,5); 
insert into order_dtls values(1234761 ,6); 
insert into order_dtls values(1234761 ,7); 
insert into order_dtls values(1234467 ,1); 
insert into order_dtls values(1234467,2); 
insert into order_dtls values(1234467 ,3); 

SELECT CUSTOMER_ID
FROM (  SELECT CUSTOMER_ID, MAX(ORDER_ID) FROM ORDER_DTLS 
        HAVING MAX(ORDER_ID)=3
        GROUP BY CUSTOMER_ID
        ORDER BY DBMS_RANDOM.value) 
WHERE ROWNUM = 1);