构建的聚合函数 collect_set （ doumented here ）让你几乎得到你想要的。它实际上可以用于你的示例输入：

  SELECT F1，collect_set（F2）
 FROM sample_table 
 GROUP BY F1 
 

不幸的是，它也删除了重复的元素，我想这不是你想要的行为。我发现奇怪的是 collect_set 存在，但没有保留重复的版本。 其他人显然认为同样的事情。它看起来像是第一个答案，第二个答案会给你你需要的UDAF。

I want to group by a given field and get the output with grouped fields. Below is an example of what I am trying to achieve:-

Imagine a table named 'sample_table' with two columns as below:-

F1  F2
001 111
001 222
001 123
002 222
002 333
003 555

I want to write Hive Query that will give the below output:-

001 [111, 222, 123]
002 [222, 333]
003 [555]

In Pig, this can be very easily achieved by something like this:-

grouped_relation = GROUP sample_table BY F1;

Can somebody please suggest if there is a simple way to do so in Hive? What I can think of is to write a User Defined Function (UDF) for this but this may be a very time consuming option.

The built in aggregate function collect_set (doumented here) gets you almost what you want. It would actually work on your example input:

SELECT F1, collect_set(F2)
FROM sample_table
GROUP BY F1

Unfortunately, it also removes duplicate elements and I imagine this isn't your desired behavior. I find it odd that collect_set exists, but no version to keep duplicates. Someone else apparently thought the same thing. It looks like the top and second answer there will give you the UDAF you need.