我找到了用laravel查询生成器解决这个问题的方法。

$latestPressureMap = DB::table('pressuremap')
        ->select('idMattress', DB::raw('MAX(created_at) as last_pressureMap_created_at'), 'presence', 'maxPressure')
        ->groupBy('idMattress');

    $mattress = DB::table('mattress')
        ->leftJoinSub($latestPressureMap, 'latest_pressureMap', function ($join) {
            $join->on('mattress.id', '=', 'latest_pressureMap.idMattress');
        })
        ->leftJoin("patient","mattress.id","=","patient.idMattress")
        ->select("patient.id", "patient.name", "patient.surname", "patient.medicalRecordNumber", "patient.visitRecordNumber", "mattress.id", "mattress.healthSystemName","mattress.building","mattress.floor","mattress.room", "mattress.bed", "patient.gender", "latest_pressureMap.presence", "latest_pressureMap.last_pressureMap_created_at","latest_pressureMap.maxPressure")
        ->where('mattress.idUser', '=', $id)
        ->get();

    return view('dashboard',['mattress' => $mattress]);