Question

我创建了一个可旋转当前表的函数，以便可以查看哪些学生喜欢什么运动。我正在使用oracle db。因此，现在，每种运动在旋转后都位于其各自的列中。如果学生喜欢该特定运动，则标记为1。

    Year    Student    Basketball    Baseball    Golf    Soccer   
    2019    Michael         1           NA         1        NA
    2018    Jason           NA          NA         1        NA
    2017    Sarah           1           1          1        NA
    2016    Michelle        NA          NA         NA       NA

我想获取体育专栏的数量，以查看有多少学生标记了该体育项目。

select 
   SUM(CASE WHEN Basketball=1 THEN 1 ELSE 0 END) as NBA,
   SUM(CASE WHEN Baseball=1 THEN 1 ELSE 0 END) as MLB,
   SUM(CASE WHEN Golf=1 THEN 1 ELSE 0 END) as PGA,
   SUM(CASE WHEN Soccer=1 THEN 1 ELSE 0 END) as MLS
from students_sports
group by year
order by 1;

我尝试了上面的语法，但是没有运气。我也尝试过以下语法。

select 
    sum(nvl("Basketball", 0)) as NBA,
    sum(nvl("Baseball", 0)) as MLB,
    etc....

运行此查询时，我得到的是行的总数，而不是标记为1的行的实际总数。

Answer 1

第一种语法是错误的。您将Basketball, Baseball, Golf, Soccer列设为varchar，因为您要将NA保存在非数字字段中。当您在查询CASE WHEN Basketball=1中进行比较时，您正在进行数值比较。因此，请按照以下方式更改查询，让我们知道它是否有效。

**Query**  
`SELECT SUM (CASE WHEN Basketball = '1' THEN 1 ELSE 0 END) AS NBA
      ,SUM (CASE WHEN Baseball = '1' THEN 1 ELSE 0 END)   AS MLB
      ,SUM (CASE WHEN Golf = '1' THEN 1 ELSE 0 END)       AS PGA
      ,SUM (CASE WHEN Soccer = '1' THEN 1 ELSE 0 END)     AS MLS
FROM students_sports
GROUP BY year
ORDER BY 1;`

示例：
https://dbfiddle.uk/?rdbms=oracle_11.2&fiddle=9c6cc6b067cc128b699316cb299769e3

This should give you result as 1 or 0. Let us know how it goes. I am not sure about your SUM what are you doing with it but it does not make sense to me as that sum will worth nothing.

旋转表格后一列中的标志计数

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