tp5.1 高级查询之 表里2字段比较大小

$map = [
    'status'        =>          1,
    'is_show'       =>          1,
];

$result = Db::name('coupon')
            ->where($map)
            ->where('total_number','exp',Db::raw('>`send_number`'))
            ->whereTime('end_time','>=',time())
            ->limit('2')
            ->select();