查找数组结构的第一个和最后一个

Question

在文件中有一个如下的数组结构。

[{"A":"1","B":"2","C":"3"},{"A":"4","B":"5","C":"6"},{"A":"7","B":"8","C":"9"}]

我该如何获取列 "A" ("1","7") 的第一个和最后一个值？需要用 Hive SQL 编写。

提前感谢您。

- sidhartha swain

Answer 1

数组的第一个元素是 array_name[0]，最后一个元素是 array_name[size(array_name)-1]。

示例：

 select example_data[0].A, example_data[size(example_data)-1].A
   from
   ( --Your example data
   select array(named_struct("A","1","B","2","C","3"),named_struct("A","4","B","5","C","6"),named_struct("A","7","B","8","C","9")) as example_data
   )s;
OK
1       7
Time taken: 2.72 seconds, Fetched: 1 row(s)

- leftjoin