Grouping hive rows in an array of this rows

问题

I have a table like the following :

User:String Alias:String
JohnDoe     John
JohnDoe     JDoe
Roger       Roger

And I would like to group all the aliases of an user in an array, in a new table which would look like this :

User:String Alias:array<String>
JohnDoe     [John, JDoe]
Roger       [Roger]

I can't figure out how to do that with HiveQL.Do I have to write an UDF for that ?

Thanks !

回答1:

Check out the built-in aggregate function collect_set.

select 
    User, 
    collect_set(Alias) as Alias
from table
group by User;

来源：https://stackoverflow.com/questions/16836702/grouping-hive-rows-in-an-array-of-this-rows