ThinkPHP distinct count 统计查询写法

下面示例是使用 ThinkPHP 6 查询数据表某个字符不重复记录的总个数：

use think\facade\Db;
...
$count_res = Db::connect('zs')->table('member_luck_log')
    ->where('set_id', $set_id)
    ->where('set_item_id', $item_id)
    ->field(Db::raw('COUNT(distinct(`vipcode`)) as `count_sum`'))
    ->find();
echo $count_res['count_sum'];