Laravel数据库操作笔记

1. 快速获得记录条数

	$medalCnt = MedalUser::select(DB::raw('count(*) as medal_cnt'))
                ->where('uid', $this->uid)
                ->where('medal_id', $medalId)
                ->value('medal_cnt');

2. 减少某项值

   $affected = Wallet::where('uid', $this->uid)->where('coin_id', 12)
       ->decrement('total',$medal['exchange_num']);
   if (!$affected) {
   
       throw new \Exception('变更失败');
   }

3. 增加某项值

   $affected = MedalUserLiveness::where(