Combine multiple rows into one space separated string

Question

So I have 5 rows like this

userid, col
--------------
1, a
1, b
2, c
2, d
3, e

How would I do query so it will look like this

Answer 1

1. MySQL with duplicates: select col1, group_concat(col2) from table1 group by col1
2. MySQL without duplicates: select col1, group_concat(distinct col2) from table1 group by col1
3. Hive with duplicates: select col1, collect_list(col2) from table1 group by col1
4. Hive without duplicates: select col1, collect_set(col2) from table1 group by col1