[英]hive sql - how to select the first n elements in hive array column and return the selected array
[英]Extract last N elements of an array in SQL (hive)
我有一个包含 arrays 的列,我想提取数组中的最后 X 个元素。
尝试提取最后两个元素的示例:
Column A
['a', 'b', 'c']
['d', 'e']
['f', 'g', 'h', 'i']
预期 output:
Column A
['b', 'c']
['d', 'e']
['h', 'i']
最好的情况是不使用 UDF
再次使用反向、分解、过滤和重新组装数组的一种方法:
with your_table as (
select stack (4,
0, array(), --empty array to check it works if no elements or less than n
1, array('a', 'b', 'c'),
2, array('d', 'e'),
3, array('f', 'g', 'h', 'i')
) as (id, col_A)
)
select s.id, collect_list(s.value) as col_A
from
(select s.id, a.value, a.pos
from your_table s
lateral view outer posexplode(split(reverse(concat_ws(',',s.col_A)),',')) a as pos, value
where a.pos between 0 and 1 --last two (use n-1 instead of 1 if you want last n)
distribute by s.id sort by a.pos desc --keep original order
)s
group by s.id
结果:
s.id col_a
0 []
1 ["b","c"]
2 ["d","e"]
3 ["h","i"]
在这个答案中使用砖房numeric_range
UDF 的更优雅的方式
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