mysql - How to combine dynamic fields and DB::raw with Laravel's fluent query builder? -

this desired sql:

select      p.id , p.title , p.msrp , i.files     , p.cost      `products` p     left join (          select              group_concat( `images`.`filename` separator ',' ) files , `product_id`                       `images`          group              `product_id`      ) on i.product_id = p.id 

here query using laravel's fluent query builder:

$products = db::table( 'products p' )     ->where( 'p.active' , '=' , 1 )     ->select( $fields )     ->get(); 

the $fields variable array of fields based on whether user logged in or not:

$fields = array( 'p.id' , 'p.title' , 'p.msrp' , 'i.files' ) ; if( auth::check() ) array_push( $fields , 'p.cost' ) ; 

i trying left join using db::raw:

->leftjoin(db::raw( "( select group_concat( images.filename separator ',' ) , product_id images group product_id ) i" , "i.product_id", "=" , "p.id" ) 

for reason not working... doing wrong? need use db::raw can group_concat multiple rows in images table delimited string.

on tangent... think sub-query select not supported if has better option, please let me know.