Hive - 如何对状态变化执行操作

Question

我的hive表中有两列。 col2包含值'Y'和'N'。在hive中我想循环遍历表，如果每次都有状态变化（从N到Y或从Y到N），我想在另一个表中插入一个新行。我如何使用hiveql做到这一点？谢谢你们！

Answer 1

insert into my_target

select  ...

from   (select  col2
               ,lag (col2) over (order by ...)  as prev_col2

        from    my_source
        ) t

where   t.col2 <>  prev_col2
;

演示

with my_source as (select posexplode(split('YYNYNNNYYY','\\B')) as (col1,col2))
select  * from my_source;

+----------------+----------------+
| my_source.col1 | my_source.col2 |
+----------------+----------------+
| 0              | Y              |
+----------------+----------------+
| 1              | Y              |
+----------------+----------------+
| 2              | N              |
+----------------+----------------+
| 3              | Y              |
+----------------+----------------+
| 4              | N              |
+----------------+----------------+
| 5              | N              |
+----------------+----------------+
| 6              | N              |
+----------------+----------------+
| 7              | Y              |
+----------------+----------------+
| 8              | Y              |
+----------------+----------------+
| 9              | Y              |
+----------------+----------------+

with my_source as (select posexplode(split('YYNYNNNYYY','\\B')) as (col1,col2))

select  *

from   (select  col1
               ,col2
               ,lag (col2) over (order by col1)  as prev_col2

        from    my_source
        ) t

where   t.col2 <>  prev_col2
;

+--------+--------+-------------+
| t.col1 | t.col2 | t.prev_col2 |
+--------+--------+-------------+
| 2      | N      | Y           |
+--------+--------+-------------+
| 3      | Y      | N           |
+--------+--------+-------------+
| 4      | N      | Y           |
+--------+--------+-------------+
| 7      | Y      | N           |
+--------+--------+-------------+