Question

我有桌费率

Key   Rate      Dt
1      2      201401
1      2      201402
1      3      201403
2      1      201308
2      2      201309 
2      1      201301

我想选择具有最低Dt的密钥和费率。

所以结果应该是这样的：

   Key   Rate      Dt
    1      2      201401
    2      1      201308

我试过了：

从Dt =的比率中选择Key，Rate，Dt（从Rates中选择MIN（dt）按键分组）

但它没有选择特定键的最低日期......你能帮帮我吗？谢谢

Answer 1

您可以使用CTE获取相关记录......

;
WITH    cteLowestDate
          AS ( SELECT   [Key]
                       ,Rate
                       ,Dt
                       ,ROW_NUMBER() OVER (PARTITION BY [Key] ORDER BY Dt) AS 'rownum'
               FROM     Rates
             )
    SELECT  [Key], Rate, Dt
    FROM    cteLowestDate
    WHERE   rownum = 1

我添加了SQL Fiddle

Answer 2

SELECT KEY,
       Rate,
       Dt
FROM   (SELECT KEY,
               Min(dt) dt
        FROM   Rates
        GROUP  BY KEY) A
       JOIN Rates B
         ON A.KEY = B.KEY
            AND A.dt = B.dt

Answer 3

我认为你的意思是：

  SELECT
    yt.key,
    yt.rate,
    yt.dt
  FROM
    (
      SELECT
        key,
        MIN(dt) AS min_dt
      FROM
        rates
      GROUP BY
        key
     ) AS kmd
     INNER JOIN rates AS yt ON
       yt.key=kmd.key AND
       yt.dt=kmd.min_dt

选择具有最低日期的值

3 个答案: