如何在SQL中计算斜率 [英] How to calculate the slope in SQL

问题描述

我在sql数据库中有一些数据，我想计算斜率.数据具有以下布局:

I have some data in a sql database and I'd like to calculate the slope. The data has this layout:

Date        |  Keyword  |  Score    
2012-01-10  |  ipad     |  0.12    
2012-01-11  |  ipad     |  0.17    
2012-01-12  |  ipad     |  0.24    
2012-01-10  |  taco     |  0.19    
2012-01-11  |  taco     |  0.34    
2012-01-12  |  taco     |  0.45    

我希望通过使用SQL创建新表来使最终输出看起来像这样:

I'd like the final output to look like this by creating a new table using SQL:

Date        |  Keyword  |  Score |  Slope    
2012-01-10  |  ipad     |  0.12  |  0.06    
2012-01-11  |  ipad     |  0.17  |  0.06    
2012-01-12  |  ipad     |  0.24  |  0.06    
2012-01-10  |  taco     |  0.19  |  0.13    
2012-01-11  |  taco     |  0.34  |  0.13    
2012-01-12  |  taco     |  0.45  |  0.13

要使事情复杂化，并非所有的关键字都具有3个日期的数据，例如，有些只有2个日期.

To complicate things, not all Keywords have 3 dates worth of data, some have only 2 for instance.

SQL越简单越好，因为我的数据库是专有的，我不太确定可用的公式，尽管我知道它可以执行OVER(PARTITION BY).谢谢！

The simpler the SQL the better since my database is proprietary and I'm not quite sure what formulas are available, although I know it can do OVER(PARTITION BY) if that helps. Thank you!

更新:我将斜率定义为excel中最适合的y = mx + p，即= slope()

UPDATE: I define the slope as best fit y=mx+p aka in excel it would be =slope()

这是我通常在excel中操作的另一个实际示例:

Here is another actual example that I usually manipulate in excel:

date        keyword         score       slope   
1/22/2012   water bottle    0.010885442 0.000334784  
1/23/2012   water bottle    0.011203949 0.000334784  
1/24/2012   water bottle    0.008460835 0.000334784  
1/25/2012   water bottle    0.010363991 0.000334784  
1/26/2012   water bottle    0.011800716 0.000334784  
1/27/2012   water bottle    0.012948411 0.000334784  
1/28/2012   water bottle    0.012732459 0.000334784  
1/29/2012   water bottle    0.011682568 0.000334784  

推荐答案

我能做的最干净的一个:

The cleanest one I could make:

SELECT
    Scores.Date, Scores.Keyword, Scores.Score,
    (N * Sum_XY - Sum_X * Sum_Y)/(N * Sum_X2 - Sum_X * Sum_X) AS Slope
FROM Scores
INNER JOIN (
    SELECT
        Keyword,
        COUNT(*) AS N,
        SUM(CAST(Date as float)) AS Sum_X,
        SUM(CAST(Date as float) * CAST(Date as float)) AS Sum_X2,
        SUM(Score) AS Sum_Y,
        SUM(Score*Score) AS Sum_Y2,
        SUM(CAST(Date as float) * Score) AS Sum_XY
    FROM Scores
    GROUP BY Keyword
) G ON G.Keyword = Scores.Keyword;

它使用简单线性回归来计算斜率.

结果:

Date         Keyword        Score         Slope
2012-01-22   water bottle   0,010885442   0,000334784345222076
2012-01-23   water bottle   0,011203949   0,000334784345222076
2012-01-24   water bottle   0,008460835   0,000334784345222076
2012-01-25   water bottle   0,010363991   0,000334784345222076
2012-01-26   water bottle   0,011800716   0,000334784345222076
2012-01-27   water bottle   0,012948411   0,000334784345222076
2012-01-28   water bottle   0,012732459   0,000334784345222076
2012-01-29   water bottle   0,011682568   0,000334784345222076

每个数据库系统似乎都有不同的方法将日期转换为数字:

Every database system seems to have a different approach to converting dates to numbers:

• MySQL :TO_SECONDS(date)或TO_DAYS(date)
• Oracle: TO_NUMBER(TO_CHAR(date, 'J'))或date - TO_DATE('1','yyyy')
• MS SQL Server: CAST(date AS float)(或等效的CONVERT)

• MySQL: TO_SECONDS(date) or TO_DAYS(date)
• Oracle: TO_NUMBER(TO_CHAR(date, 'J')) or date - TO_DATE('1','yyyy')
• MS SQL Server: CAST(date AS float) (or equivalent CONVERT)

这篇关于如何在SQL中计算斜率的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！