提取HIVE中數組的最後兩個元素

Question

我在配置單元表中有一個數組，我想提取每個數組的兩個最後一個元素，如下所示： [「a」，「b」，「c 「] - > [」 b」， 「C」]

我試着像這樣的代碼：

SELECT 
*, 
array[size]  AS term_n, 
array[size - 1] AS term_n_1 
FROM 
(SELECT *, size(array) AS size FROM MyTable); 

但它沒有工作，有人有什麼想法嗎？

Answer 1

我不知道，你所得到的錯誤，但它應該是類似

select 
yourarray[size(yourarray)], 
yourarray[size(yourarray)-1] 
from mytable 

Answer 2

1. array是保留字，應該合格。
2. 內部子查詢應該是別名。
3. 數組索引從0開始，如果該數組的大小是5，那麼最後一個索引是4

---

演示

with MyTable as (select array('A','B','C','D','E') as `array`) 

SELECT * 
     ,`array`[size - 1] AS term_n 
     ,`array`[size - 2] AS term_n_1 

FROM (SELECT * 
       ,size(`array`) AS size 

     FROM MyTable 
     ) t 
; 

---

+-----------------------+--------+--------+----------+ 
|  t.array  | t.size | term_n | term_n_1 | 
+-----------------------+--------+--------+----------+ 
| ["A","B","C","D","E"] |  5 | E  | D  | 
+-----------------------+--------+--------+----------+