取出一个满足 A 条件, B 字段倒序的集合, 怎么解? 求思路。

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This topic created in 4326 days ago, the information mentioned may be changed or developed.

想取出各个name的最新的dateline所在记录的集合。

字段

dateline

集合

11 replies • 2014-11-21 22:22:54 +08:00

incompatible

Nov 21, 2014

select name, max(dateline) from t group by name

vook

Nov 21, 2014

@incompatible 各个 name 的最新的 dateline 所在记录，还包括 id 等其他的字段。

xlmo

Nov 21, 2014

SELECT * FROM table GROUP BY `name` ORDER BY dateline DESC

yanleijava

Nov 21, 2014

你指的是Group By排序，参考 http://iyanlei.com/hive_groupby_order.html

staticor

Nov 21, 2014

@vook selct * from
(select name, max(dateline) as maxdate from t group by name)
natura left join (
select name, dateline as maxdateline , id ...
from t
)

?这样试试

vook

Nov 21, 2014

@xlmo 你这取的是默认排序 name 的第一条记录, 再对 dateline 排序。

我想要的是对时间排序后的第一条记录。

vook

Nov 21, 2014

@yanleijava

SELECT * FROM (SELECT * FROM t1 ORDER BY dateline DESC) as t2 GROUP BY `name`;

就是这个。谢谢！学习了！

laoyuan

Nov 21, 2014

嗯，只能这样我也是这么写的

laoyuan

Nov 21, 2014

不过后来我觉得分两条写也无所谓

alsotang

Nov 21, 2014

呃，楼上全是乱来。你们就不懂有个叫 window function 的东西存在 sql 中吗

Fedor

Nov 21, 2014

SELECT group_concat(id order by dateline desc SEPARATOR '') AS id FROM table group by game_id;