如何在laravel 4.2中编写这个sql命令

I'm trying to run this query with Laravel 4.2 but I'm unsure how to implement it. Can anyone give me a pointer in the right direction? Thanks!

select * from (select * from `t_quotation_revises` ORDER BY id DESC) AS x GROUP BY `t_quotation_id`

select * from (select * from t_quotation_revises ORDER BY id DESC) AS x GROUP BY t_quotation_id

This above query would be written as in laravel 4.2 like :

$reviseQuotationArr = DB::table(DB::raw('(select * from t_quotation_revises ORDER BY id DESC)AS x')) ->groupBy('t_quotation_id') ->get();