Jak obliczyć nachylenie w SQL

Najczystszy, jaki mogłem zrobić:

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(CAST(Date as float) * Score) AS Sum_XY
    FROM Scores
    GROUP BY Keyword
) G ON G.Keyword = Scores.Keyword;

Używa Prosta regresja liniowa aby obliczyć nachylenie.

Wynik:

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

Każdy system baz danych wydaje się mieć inne podejście do konwersji dat na liczby:

• MySQL: TO_SECONDS(date) lub TO_DAYS(date)
• Wyrocznia: TO_NUMBER(TO_CHAR(date, 'J')) lub date - TO_DATE('1','yyyy')
• Serwer MS SQL: CAST(date AS float) (lub odpowiednik CONVERT )