hive union all 使用

功能：将两个表中的 同样的字段拼接到一起

測试：

create external table IF NOT EXISTS temp_uniontest_ta
(
a1 string,
a2 string
)
partitioned by (dt string)
row format delimited fields terminated by '\t'
stored as textfile;
ALTER TABLE temp_uniontest_ta ADD IF NOT EXISTS PARTITION (dt = '2014-10-13') location '/temp/unionTest/ta/';
a1	a2	2014-10-13
b1	b2	2014-10-13
c1	c2	2014-10-13

create external table IF NOT EXISTS temp_uniontest_tb
(
a1 string,
a2 string
)
partitioned by (dt string)
row format delimited fields terminated by '\t'
stored as textfile;
ALTER TABLE temp_uniontest_tb ADD IF NOT EXISTS PARTITION (dt = '2014-10-13') location '/temp/unionTest/tb/';
d1	d2	2014-10-13
e1	e2	2014-10-13

select * from 
(
select a1,a2 from temp_uniontest_ta where dt = '2014-10-13'
union all
select a1,a2 from temp_uniontest_tb where dt = '2014-10-13'
)tmp;

a1	a2
b1	b2
c1	c2
d1	d2
e1	e2