select distinct c0,c1,c3 from t t1 where t1.c3='Y' UNION SELECT DISTINCT c0,c1,c3 from t t2 where t2.c3='N' and not exists(select 1 from t t3 where t3.c0=t2.c0 and t3.c1=t2.c1 and t3.c3='Y' )
select C0,C1,DECODE(SUM(DECODE(C3,'Y',1)),0,'N','Y') C3 FROM T GROUP BY C0,C1
select * from (select C0,C1,MAX(C3) over(partition by C0,C1) C3 from test) group by C0,C1,C3;
UNION
SELECT DISTINCT c0,c1,c3 from t t2 where t2.c3='N' and not exists(select 1 from t t3 where t3.c0=t2.c0 and t3.c1=t2.c1 and t3.c3='Y' )
FROM T
GROUP BY C0,C1