将不同数量的行分组为Hive表中的列 [英] Group varying number of rows as columns in Hive table

问题描述

我有一个Hive表，其中包含用户标识和一些变量选项，基本如下所示：

I have a Hive table that contains userIDs and some variable choice, and basically looks like this:

userID    selection
   1          A
   1          D
   1          F
   2          A
   2          C

我想要做的就是浓缩这些信息，最终得到如下结果：

What I would like to do is condense this information and end up with something like:

 userID    selection1    selection2    selection3
    1          A             D              F
    2          A             C

这甚至可能吗？我不清楚怎么做这个分组，因为可能的选择数量随用户而异。

Is this even possible? It isn't clear to me how to do this grouping, given that the number of possible selections varies with the user.

如果我能做点什么如：

It would even be fine if I could do something like:

 userID    selection 
    1        A,D,F    
    2         A,C     

我尝试了几种方法，但至今没有足够的描述。我想我想要的是以下形式：

I have tried several approaches but so far nothing has been close enough to describe. I think what I want is something of the form:

select userID, group_concat(selection) from table_name group by userID

但是据我所知，group_concat函数不可用。

but as far as I can tell the group_concat function isn't available.

谢谢！

Thanks!

推荐答案

如果任何人最终需要答案这可以通过以下方式实现：

In case anyone ends up needing the answer to this, it can be achieved via:

select userID, collect_set(selection) from table_name group by userID

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