thinkphp6 leftjoin联表查询时，子表有多条记录去重后获取子表的最新记录查询方法

//构建子查询
$ct_sql= Db::name('CustomerTrace')->order('id desc')->buildSql();
$rows = empty($param['limit']) ? get_config('app.page_size') : $param['limit'];
$content = CustomerList::where($where)
    ->field('a.*,ct.follow_time,ct.next_time')
    ->alias('a')
    ->join($ct_sql.' ct', 'ct.cid = a.id','LEFT')
    ->order($orderby)
    ->group('ct.follow_time') //去重
    ->paginate($rows, false, ['query' => $param]);