SQL - 嵌套聚集

Question

我有这样的：

SELECT BRAND_ID, CAST (ROUND (AVG(PROD_PRICE), 2) AS NUMERIC (9, 2)) AS 'LARGEST AVERAGE' 
    FROM LGPRODUCT 
    GROUP BY BRAND_ID 

，它显示了一堆的均价，每个品牌，就像它应该。

但是如果我只想显示最高的数字呢？还是最低？

我一直试图在各种不同的方式使用MAX，并尝试使用WHERE和HAVING。

我错过了什么？

Answer 1

由于您提到了RDBMS，以下查询将适用于大多数rdbms。上述查询的

SELECT BRAND_ID, 
     CAST (ROUND (AVG(PROD_PRICE), 2) AS NUMERIC (9, 2)) AS 'LARGEST AVERAGE' 
FROM LGPRODUCT 
GROUP BY BRAND_ID 
HAVING CAST (ROUND (AVG(PROD_PRICE), 2) AS NUMERIC (9, 2)) = 
     (
      SELECT MAX(xx) 
      FROM 
      (
       SELECT CAST (ROUND (AVG(PROD_PRICE), 2) AS NUMERIC (9, 2)) as xx 
       FROM LGPRODUCT 
       GROUP BY BRAND_ID 
      ) s 
     ) 

一个优点是它处理的重复（具有BRAND_ID S中的最大平均）