有沒有什麼辦法來存儲查詢中的值，然後在下面的查詢中使用它？

Question

我有一個Postgres SQL數據庫，有測驗，問題，答案和標記在那裏（多個表）我試圖編寫一個查詢來計算一個測驗的最高分，然後使用剛剛計算出的查詢來更新測驗表最高分

我的繼承人querys

SELECT SUM(maxscore) 
FROM (
    SELECT max(answer.answermark) AS maxscore 
    FROM answer, questions 
    WHERE questions.quizid = 1 AND answer.questionid = questions.questionid 
    GROUP BY answer.questionid 
) scr; 

UPDATE quiz 
SET maxscore = '50' 
WHERE quizid = 1 

其中「SET maxscore = '50'」我需要的不是鍵入50，我需要使用計算從上面的查詢，有什麼辦法？

感謝

Answer 1

嘗試CTE：

with v as (
SELECT SUM(maxscore) 
FROM (
    SELECT max(answer.answermark) AS maxscore 
    FROM answer, questions 
    WHERE questions.quizid = 1 AND answer.questionid = questions.questionid 
    GROUP BY answer.questionid 
) 
UPDATE quiz 
SET maxscore = v.sum 
from v 
WHERE quizid = 1 

Answer 2

在這種情況下，你並不需要保持狀態。做到在from條款：

update quiz 
set maxscore = scr.maxscore 
from (
    select sum(maxscore) as maxscore 
    from (
     select max(a.answermark) as maxscore 
     from 
      answer a 
      inner join 
      questions q using (questionid) 
     where q.quizid = 1 
     group by questionid 
    ) s 
) scr 
where quizid = 1 

如果你想這樣做的所有quizid：

update quiz 
set maxscore = scr.maxscore 
from (
    select quizid, sum(maxscore) as maxscore 
    from (
     select quizid, max(a.answermark) as maxscore 
     from 
      answer a 
      inner join 
      questions q using (questionid) 
     group by quizid, questionid 
    ) s 
    group by quizid 
) scr 
where quiz.quizid = scr.quizid