我有一个Feed应用程序，我试图对连续的结果进行分组。我的表看起来像这样:postid|posttype|target|action|date|title|content1|userid|NULL|upgrade|0000-01-0000:00:00|Upgraded1|exmple1|userid|NULL|upgrade|0000-01-0000:00:01|Upgraded2|exmple1|userid|NULL|downgrade|0000-01-0000:00:02|Downgraded|exmple1|userid|NULL|upgrade|0000-01-0000:00