使用 SQL windows 分析函数计算百分比变化

Question

我正在使用下面的 table 计算某个科目在学期内总分的百分比变化。

name  subject  session     term  totalscore
-------------------------------------------
jack  maths    2013/2014    1      70
jack  eng      2013/2014    1      65
jack  science  2013/2014    1      80
jack  maths    2013/2014    2      72
jack  eng      2013/2014    2      87
jack  science  2013/2014    2      67
jack  maths    2013/2014    3      70
jack  eng      2013/2014    3      70
jack  science  2013/2014    3      85

我尝试使用如下所示的 windows LAG 函数来计算总分百分比变化，但在 percentage_change 列

中得到 NULL 值

SELECT
    name,
    subject,
    term,
    session,
    totalscores -  lag(totalscores, 1) over(partition by subject, session, term order by session, term) / 100*100
FROM
    totalscore
GROUP BY
    name, subject, session, term, totalscores
ORDER BY 
    term

预期结果 table 看起来像这样

name  subject  session     term  totalscore   percent_change
------------------------------------------------------------
jack  maths    2013/2014    1      70           null
jack  eng      2013/2014    1      65           null
jack  science  2013/2014    1      80           null  
jack  maths    2013/2014    2      72           2%
jack  eng      2013/2014    2      87           22%
jack  science  2013/2014    2      67          -5%
jack  maths    2013/2014    3      70          -2%
jack  eng      2013/2014    3      70          -17%
jack  science  2013/2014    3      85           16%

有什么方法可以帮助修复这个错误吗？我将不胜感激我能得到的任何帮助。谢谢。

Answer 1

您似乎只想要差异（因为这些已经是百分比）。但关键是让 partition by 正确对应 lag():

select name, subject, term, session,
       (totalscores -
        lag(totalscores) over(partition by name, subject order by session, term)
       ) as diff
from totalscore
order by name, subject, session, term;

使用 SQL windows 分析函数计算百分比变化

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