laravel的原生子查询，用来统计3张表的相关数据

$goods=DB::select('SELECT COUNT(gn.rfid) as num,pro.* FROM goods_nexus
as gn RIGHT JOIN (SELECT g.* ,gc.class_name FROM goods as
g LEFT JOIN goods_class as gc  ON g.class_id = gc.id)as pro ON pro.id = gn.goods_id GROUP BY pro.id ASC')
;

dd($goods);

下面是搜索条件的拼接：

public function index(Request $request){
$name=$request->input('name');
$where = ' WHERE 1';
if ($name){
$where = ' WHERE name like ' ."'%$name%'";
}
$goods=DB::select('SELECT COUNT(gn.rfid) as nums,pro.* FROM goods_nexus
as gn RIGHT JOIN (SELECT g.* ,gc.class_name FROM goods as
g LEFT JOIN goods_class as gc  ON g.class_id = gc.id)as pro ON
pro.id = gn.goods_id '.$where.' GROUP BY pro.id ASC');
return view('index')
->with('goods',$goods);
}