如何从结果中获取最新行？

Question

我有这个查询

SELECT ann_arr.id,ann_arr.user_id,ann_arr.date,ann_arr.time,
ann_arr.venue_id
FROM ann_arr
WHERE user_id
IN (SELECT DISTINCT n2.mem_id AS frnd FROM network n1,network n2 WHERE n1.frd_id=n2.mem_id AND n1.mem_id='329' AND n2.frd_id='329') 
AND ann_arr.user_id !='329'
ORDER BY DATE DESC,TIME DESC

我的结果为

id  user_id date    time    venue_id
995 399 2012-02-02  12:37:30    56
994 399 2012-02-02  12:36:06    56
993 399 2012-02-02  12:35:15    56
992 399 2012-02-02  12:32:40    56
991 399 2012-02-02  12:26:17    56
990 399 2012-02-02  12:23:06    56
989 399 2012-02-02  12:21:52    56
968 693 2012-01-25  13:27:11    1016

我想要的结果必须包含唯一的用户ID，最后id用户399 ID将955

*注 SELECT DISTINCT n2.mem_id AS frnd FROM network n1,network n2 WHERE n1.frd_id=n2.mem_id AND n1.mem_id='329' AND n2.frd_id='329'将包含用户朋友ids说'399','693'等

//预期答案

id  user_id date    time    venue_id
995 399 2012-02-02  12:37:30    56
968 693 2012-01-25  13:27:11    1016

请帮助

感谢

Answer 1

如果我已正确理解，您需要按user_id进行分组：

SELECT ann_arr.id,ann_arr.user_id,ann_arr.date,ann_arr.time,
ann_arr.venue_id
FROM ann_arr
WHERE user_id
IN (SELECT DISTINCT n2.mem_id AS frnd FROM network n1,network n2 WHERE n1.frd_id=n2.mem_id AND n1.mem_id='329' AND n2.frd_id='329') 
AND ann_arr.user_id !='329'
GROUP BY ann_arr.user_id
ORDER BY DATE DESC,TIME DESC

Answer 2

你应该试试GROUP BY user_id，＆amp;改变日期的顺序。

Answer 3

将id DESC添加到ORDER BY子句中。