仅选择多行的最大值记录

Question

我有一张表，其中包含

等记录

Unit    Rate    Date-effected
-------------------------------------------
ALHA    ILS     2014-03-02 00:00:00.000
ALHA    ILS     2014-08-02 00:00:00.000
BUCK    ILS     2013-02-14 00:00:00.000
BUCK    ILS     2014-03-02 00:00:00.000
BUCK    ILS     2014-08-02 00:00:00.000
CASC    ILD     2013-02-14 00:00:00.000
CASC    ILD     2014-03-02 00:00:00.000
CASC    ILD     2014-08-02 00:00:00.000   

现在，我只想在结果table中选择最大日期值记录。是，

Unit    Rate    DateEffected
-------------------------------------------
ALHA    ILS     2014-08-02 00:00:00.000
BUCK    ILS     2014-08-02 00:00:00.000
CASC    ILD     2014-08-02 00:00:00.000   

Answer 1

希望这有帮助。

0 path

Answer 2

您可以使用ROW_NUMBER：

SELECT Unit, Rate, DateEffected
FROM (
  SELECT Unit, Rate, DateEffected,
         ROW_NUMBER() OVER (PARTITION BY Unit 
                            ORDER BY DateEffected DESC) AS rn
FROM mytable) AS t
WHERE t.rn = 1