如何从子查询返回的一组值中检索最小值

Question

以下子查询：

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

返回以下值：

MID   AVGSTARS

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

现在我必须从这个恰好是的中间结果中检索最小值

MID   AVGSTARS

104    2.5000
103    2.5000

为了实现这一点，我编写了以下不起作用的查询：

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，但我想在这些行上写一个查询。谁能帮帮我。

谢谢。

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

编辑：

8.0 之前的 MySQL：

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)