hive on spark combine equivalent work get wrong result because of TS operation compare

create table a1(KEHHAO string, START_DT string) partitioned by (END_DT string);
create table a2(KEHHAO string, START_DT string) partitioned by (END_DT string);

alter table a1 add partition(END_DT='20161020');
alter table a1 add partition(END_DT='20161021');

insert into table a1 partition(END_DT='20161020') values('2000721360','20161001');


SELECT T1.KEHHAO,COUNT(1) FROM ( 
SELECT KEHHAO FROM a1 T 
WHERE T.KEHHAO = '2000721360' AND '20161018' BETWEEN T.START_DT AND T.END_DT-1 
UNION ALL 
SELECT KEHHAO FROM a2 T
WHERE T.KEHHAO = '2000721360' AND '20161018' BETWEEN T.START_DT AND T.END_DT-1 
) T1 
GROUP BY T1.KEHHAO 
HAVING COUNT(1)>1; 

+-------------+------+--+
|  t1.kehhao  | _c1  |
+-------------+------+--+
| 2000721360  | 2    |
+-------------+------+--+