如何使用 2 列的結果在 Oracle sql 中創建計算列

Question

我與 oracle sql 堆疊我有 4 列課程，性別，總注冊，總通過（最后 2 列是計算出來的，在數據庫中不存在）

我正在嘗試創建第 5 列來計算 (Total Pass / Total Enrolled) *100 的結果我使用了以下 sql

select Course , Gender",
       Count( case
       when Grade In('A+','A-','B','B+','B-','C','C+''F') then 'Total Enrolled with grades’ 
end ) as "Total_Enrolled",
       Count ( case
              when Grade In ('A+','A-','B','B+','B-','C','C+') then 'Pass'
       end ) as "Total_Pass"
  from Result
 group by 
          Course,
         Gender
 order by Course

感謝你的幫助

謝謝

Answer 1

嗯。 . . 這聽起來像條件聚合：

select Course, Gender,
       sum(case when Grade In ('A+', 'A-', 'B', 'B+', 'B-', 'C', 'C+', 'F') 
               then 1 else 0
           end) as Total_Enrolled
       sum(case when Grade In ('A+', 'A-', 'B', 'B+', 'B-', 'C', 'C+') 
               then 1 else 0
           end) as Total_Passed,
       ( sum(case when Grade In ('A+', 'A-', 'B', 'B+', 'B-', 'C', 'C+') 
                  then 1 else 0
              end) /
         sum(case when Grade In ('A+', 'A-', 'B', 'B+', 'B-', 'C', 'C+', 'F') 
                  then 1 
             end)
       ) as pass_ratio
from Result
group by Course, Gender
order by Course;

如果您可以在WHERE子句中進行過濾，這將大大簡化：

select Course, Gender,
       count(*) as Total_Enrolled
       sum(case when Grade In ('A+', 'A-', 'B', 'B+', 'B-', 'C', 'C+') 
               then 1 else 0
           end) as Total_Passed,
       avg(case when Grade In ('A+', 'A-', 'B', 'B+', 'B-', 'C', 'C+') 
                then 1
            end) as pass_ratio
from Result
where Grade In ('A+', 'A-', 'B', 'B+', 'B-', 'C', 'C+', 'F')
group by Course, Gender
order by Course;

Answer 2

一個簡單的選擇是將當前查詢用作 CTE，然后重用其計算列來獲得最終結果：

WITH
   temp
   AS
      (  SELECT course,
                gender,
                COUNT (CASE
                          WHEN grade IN ('A+',
                                         'A-',
                                         'B',
                                         'B+',
                                         'B-',
                                         'C',
                                         'C+',
                                         'F')
                          THEN
                             'Total Enrolled with grades'
                       END) AS total_enrolled,
                COUNT (CASE
                          WHEN grade IN ('A+',
                                         'A-',
                                         'B',
                                         'B+',
                                         'B-',
                                         'C',
                                         'C+')
                          THEN
                             'Pass'
                       END) AS total_pass
           FROM result
       GROUP BY course, gender)
  SELECT course,
         gender,
         total_enrolled,
         total_pass,
         --
         (total_pass / total_enrolled) * 100 AS fifth_column
    FROM temp
ORDER BY course

或者，您可以重新輸入這些CASE並在同一個查詢中執行，但這有點難以閱讀。

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順便說一句，就像他們在2001 年所說的：太空漫游：“到處都是星星”。 您的代碼充滿了錯誤。 在這里發布內容時應該更加小心。