ThinkPHP使用distinct和group by去重复的数据

在一对多关联查询中，遇到重复数据的问题，这不是我们想要的结果，下面就是两种常用的去重方法。 

1、distinct方法去重

$data=$test_data->Distinct(true)->field('descriprion')->order('description desc')->select();
 

2、group方法去重

$items = Suspect::alias('s')
    ->leftJoin("activity a","a.suspect_id = s.id")
    ->field("s.*,a.id as activity_id")
    ->group('id')
    ->select();
Mysql语句：

SELECT `s`.*,a.id as activity_id FROM `suspect` `s` LEFT JOIN `activity` `a` ON `a`.`suspect_id`=`s`.`id` GROUP BY `id`