我怎樣才能得到我的表中每一天的字數

Question

我需要編寫一個sql語句來獲取表中每一天的WPM計數。它有幾天會有 多個條目;我只需要最高的WPM。此外，不包括空條目。

The data set should look like: 
Date_completed, Max_WPM 
date here, wpm 
date here, wpm 

SELECT 
     DISTINCT A.DATE_COMPLETED 
      ,A.WPM Max_WPM 
FROM KEYBOARD_LEARNING A 

我想過濾哪裏只有不同的日子返回這個表的結果集。但上述查詢不起作用。我怎樣才能返回與WPM不同的日期？

DATE_completed MAX_WPM 
--------------------------  --------------- 
7/12/2012    ... 
7/12/2012    .... 
7/12/2012 
7/22/2012 
7/6/2012 
7/12/2012 
7/12/2012 
7/6/2012 
7/12/2012 
7/12/2012 
7/6/2012 
7/6/2012 
6/13/2012 
7/12/2012 
7/12/2012 
7/16/2012 
6/6/2012 
7/6/2012 
7/6/2012 
6/12/2012 
6/13/2012 
7/6/2012 
7/6/2012 
7/6/2012 
7/12/2012 
6/13/2012 
7/4/2012 
6/14/2012 
7/6/2012 

Answer 1

這聽起來像你想

SELECT A.DATE_COMPLETED 
     ,MAX(A.WPM) Max_WPM 
    FROM KEYBOARD_LEARNING A 
WHERE a.wpm IS NOT NULL 
GROUP BY a.date_completed 

這假定沒有DATE_COMPLETED值有一個時間的組成部分。如果是這樣，你需要TRUNC日期

SELECT TRUNC(A.DATE_COMPLETED) date_completed 
     ,MAX(A.WPM) Max_WPM 
    FROM KEYBOARD_LEARNING A 
WHERE a.wpm IS NOT NULL 
GROUP BY TRUNC(a.date_completed)