取出一个满足 A 条件, B 字段倒序的集合, 怎么解? 求思路。 - V2EX
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vook
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取出一个满足 A 条件, B 字段倒序的集合, 怎么解? 求思路。

  •  
  •   vook 2014-11-21 10:25:06 +08:00 3364 次点击
    这是一个创建于 4058 天前的主题,其中的信息可能已经有所发展或是发生改变。
    
    想取出各个name的最新的dateline所在记录的集合。
    11 条回复    2014-11-21 22:22:54 +08:00
    incompatible
        1
    incompatible  
       2014-11-21 10:31:54 +08:00   1
    select name, max(dateline) from t group by name
    vook
        2
    vook  
    OP
       2014-11-21 10:35:34 +08:00
    @incompatible 各个 name 的最新的 dateline 所在记录, 还包括 id 等其他的字段。
    xlmo
        3
    xlmo  
       2014-11-21 10:37:28 +08:00   1
    SELECT * FROM table GROUP BY `name` ORDER BY dateline DESC
    yanleijava
        4
    yanleijava  
       2014-11-21 10:52:27 +08:00   1
    你指的是Group By排序,参考 http://iyanlei.com/hive_groupby_order.html
    staticor
        5
    staticor  
       2014-11-21 10:55:30 +08:00   1
    @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
        6
    vook  
    OP
       2014-11-21 11:06:02 +08:00
    @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
        7
    vook  
    OP
       2014-11-21 11:36:13 +08:00
    @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
        8
    laoyuan  
       2014-11-21 12:41:01 +08:00
    嗯,只能这样我也是这么写的
    laoyuan
        9
    laoyuan  
       2014-11-21 12:41:34 +08:00
    不过后来我觉得分两条写也无所谓
    alsotang
        10
    alsotang  
       2014-11-21 13:34:21 +08:00   1
    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
        11
    Fedor  
       2014-11-21 22:22:54 +08:00
    SELECT group_concat(id order by dateline desc SEPARATOR '') AS id FROM table group by game_id;
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