在 Hive 中，如何组合多个表以生成包含对象数组的单行？

Posted 2023-04-18

【中文标题】在 Hive 中，如何组合多个表以生成包含对象数组的单行？

【英文标题】：In Hive, how to combine multiple tables to produce single row containing array of objects?

【发布时间】：2019-05-11 07:54:41

【问题描述】：

我有两张表如下：

users table
==========================  
| user_id   name     age |  
|=========================  
|  1        pete      20 |  
|  2        sam       21 |  
|  3        nash      22 |  
==========================

hobbies table
======================================
| user_id   hobby         time_spent |
|=====================================
|  1        football          2      |
|  1        running           1      |
|  1        basketball        3      |
======================================

第一个问题：我想做一个可以以这种格式返回行的 Hive 查询：

 "user_id":1, "name":"pete", "hobbies":[ hobby: "football", "time_spent": 2, "hobby": "running", "time_spent": 1, "hobby": "basketball", "time_spent": 3 ] 

第二个问题：如果爱好表如下：

========================================
| user_id   hobby             scores   |
|=======================================
|  1        football          2,3,1    |
|  1        running           1,1,2,5  |
|  1        basketball        3,6,7    |
========================================

是否有可能获得如下所示的输出中 score 是列表的行输出：

 "user_id":1, "name":"pete", "hobbies":[ hobby: "football", "scores": [2, 3, 1], "hobby": "running", "scores": [1, 1, 2, 5], "hobby": "basketball", "scores": [3, 6, 7] ] 

【参考方案1】：

我找到了第一个问题的答案

select u.user_id, u.name, 
       collect_list(
           str_to_map(
                concat_ws(",", array(
                    concat("hobby:", h.hobby), 
                    concat("time_spent:", h.time_spent)
                ))
           )
       ) as hobbies
from users as u
join hobbies as h on u.user_id=h.user_id
group by u.user_id, u.name;