如何檢索由子查詢

Question

下面的子查詢返回一組值的最小值（S）：

SELECT R.mID AS MID, AVG(R.stars) AS AVGSTARS FROM Rating R 
GROUP BY R.mID 
ORDER BY AVGRSTARS 

返回下列值：

MID AVGSTARS 

104 2.5000 
103 2.5000 
101 3.0000 
108 3.3333 
107 4.0000 
106 4.5000 

現在我要檢索最小值（或多個）從其中發生該中間結果是

MID AVGSTARS 

104 2.5000 
103 2.5000 

爲了實現這一點，我已經寫後續ing查詢不工作：

SELECT INTER1.RMID FROM 
(SELECT R.mID AS MID, AVG(R.stars) AS AVGSTARS FROM Rating R 
GROUP BY R.mID 
ORDER BY AVGRSTARS) INTER1 
WHERE MIN(AVGRSTARS) = INTER1.AVRSTARS 

我知道它不起作用，但我想寫一個查詢這些行。有人能幫幫我嗎。

謝謝。

Answer 1

你可以使用：

WITH cte AS ( 
    SELECT R.mID AS MID, AVG(R.stars) AS AVGSTARS 
    FROM Rating R GROUP BY R.mID) 
SELECT MID, AVGSTARS 
FROM cte 
WHERE AVGSTARS = (SELECT MIN(AVGSTARS) FROM cte); 

DBFiddle Demo

編輯：

的MySQL前8.0：

SELECT MID, AVGSTARS 
FROM (SELECT R.mID AS MID, AVG(R.stars) AS AVGSTARS 
     FROM Rating R GROUP BY R.mID) sub 
WHERE AVGSTARS = (SELECT MIN(AVGSTARS) 
        FROM (SELECT R.mID AS MID, AVG(R.stars) AS AVGSTARS 
         FROM Rating R GROUP BY R.mID) AS s)