Question

I want to perform :group and :order on my module, since Mysql does group by before order by you get mixed results and not what you expected.

the SQL solution for that would be:

SELECT * FROM 

(
select * from `my_table` order by timestamp desc
) as my_table_tmp

group by catid

order by nid desc

how can I write that in ruby using activerecord?

Answer 1

I think you can just use the Arel methods directly:

MyTable.from("(SELECT * FROM my_table ORDER BY timestamp DESC) as my_table").group(:catid).order("nid DESC")