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google-bigquery - 在 BigQuery 中使用 Where 子句进行切片

问题描述

我的查询有问题，试图计算术语和会话之间的分数变化，每次我尝试按会话切片时，如下面的查询所示，更改列在所有行中返回“null”，但如果我删除会话切片，更改列返回所需的值。

卡表

name  id  subject session   term classroom ca_cat  score
one   1    maths  2018/2019   1    level1    1       10
one   1    maths  2018/2019   1    level1    2       6
two   2    maths  2018/2019   1    level1    1       9
two   2    maths  2018/2019   1    level1    2       7
one   1    maths  2018/2019   2    level1    1       9
one   1    maths  2018/2019   2    level1    2       8
two   2    maths  2018/2019   2    level1    1       7
two   2    maths  2018/2019   2    level1    2       5

考试桌

name    id    course session   term classroom    score
one     1      maths 2018/2019   1    level1      50
two     2      maths 2018/2019   1    level1      49 
one     1      maths 2018/2019   2    level1      50
two     2      maths 2018/2019   2    level1      50

询问

select
    studentid,
    name,
    subject,
    classroom,
    session,
    term,
    round(avg_score,0) as average_score,
    round(avg_score -  lag(avg_score, 1) over(partition by name, subject order by session) / 100*100, 0) as change,
from (
    select studentid, name, subject, classroom, session, term, avg(totalscore) over(partition by name, classroom, session, term) avg_score
    from (
    SELECT name, studentid, subject, classroom, session, term, caone, catwo, exam,
  caone + catwo + exam AS totalscore
FROM (
  SELECT name, studentid, subject, classroom, session, term, 
    MAX(IF(cacount = 1, ca.score, NULL)) AS caone,
    MAX(IF(cacount = 2, ca.score, NULL)) AS catwo,
    ANY_VALUE(ex.score) AS exam
  FROM `exam` ex
  JOIN `catable` ca
  USING (name, studentid, subject, classroom, session, term) 
  GROUP BY name, studentid, subject, classroom, session, term
)  
    ))
    where studentid=1 and session='2018/2019' and term=2
group by studentid, name, subject, classroom, session,term, avg_score

我的预期输出是这样的

name, id, subject, classroom, session,    term, totalscore change
one    1    math    level1     2018/2019   1        66       null
one    1    math    level1     2018/2019   2        67        1 
two    2    math    level1     2018/2019   1        65       null
two    2    math    level1     2018/2019   2        62       -3

分数的变化是术语之间的差异，例如 2nd-1st 和 3rd-2nd

有解决方法吗？我已经尝试了所有我所知道的似乎无法找到为什么它会以这种方式响应或问题可能是什么。

标签： google-bigquerysubqueryanalytics

解决方案

以下是 BigQuery 标准 SQL

#standardSQL
SELECT *, 
  totalscore - LAG(totalscore) OVER(PARTITION BY name, id, subject, classroom, session ORDER BY term) AS change
FROM (
  SELECT name, id, subject, classroom, session, term, caone + catwo + exam AS totalscore
  FROM (
    SELECT name, id, subject, classroom, session, term, 
      MAX(IF(ca_cat = 1, ca.score, NULL)) AS caone,
      MAX(IF(ca_cat = 2, ca.score, NULL)) AS catwo,
      ANY_VALUE(ex.score) AS exam,
    FROM `project.dataset.exam` ex
    JOIN `project.dataset.catable` ca
    USING (name, id, subject, classroom, session, term) 
    GROUP BY name, id, subject, classroom, session, term 
  )
)
-- ORDER BY name, id, subject, classroom, session, term

当应用于您问题的样本数据时 - 结果是

Row name    id  subject classroom   session     term    totalscore  change   
1   one     1   maths   level1      2018/2019   1       66          null     
2   one     1   maths   level1      2018/2019   2       67          1    
3   two     2   maths   level1      2018/2019   1       65          null     
4   two     2   maths   level1      2018/2019   2       62          -3

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