SQL INNER JOIN实体

Question

我想执行这个查询：

-- The most expensive item sold ever 
SELECT 
    c.itemID, c.itemName 
FROM 
    item AS c 
JOIN 
    (SELECT 
     b.itemID as 'itemid', MAX(b.item_initialPrice) AS 'MaxPrice' 
    FROM 
     buyeritem AS a 
    INNER JOIN 
     item AS b ON a.item_ID = b.itemID) AS d ON c.itemID = d.itemid 
GROUP BY 
    c.itemID, c.itemName; 

我item表看起来像这样：

create table item 
(
    itemID int IDENTITY(1000, 1) NOT NULL, 
    itemName varchar(15) NOT NULL, 
    Item_desc varchar(255), 
    Item_initialPrice MONEY, 
    ItemQty int, 
    ownerID int NOT NULL, 
    condition varchar(20) NOT NULL, 

    PRIMARY KEY (itemID), 

    FOREIGN KEY (ownerID) REFERENCES seller (sellerID) 
); 

的问题是，列item.itemID无效在选择列表中，因为它是不包含在聚合函数或GROUP BY子句中。我试图在末尾添加一个group by子句

group by c.itemID, c.itemName 

但是我仍然得到同样的错误？我真的不知道问题来自哪里。

我也有这个疑问

-- The most active seller(the one who has offered the most number of items) 
SELECT 
    a.ownerID, b.sellerName 
FROM 
    item AS a 
INNER JOIN 
    seller AS b ON a.ownerID = b.sellerID 
GROUP BY 
    a.ownerID, b.sellerName 
ORDER BY 
    COUNT(a.itemID) DESC; 

我想补充itemQty与item表ownerID和sellerName上述以来，这将是实现这一最好的方法是什么？

Answer 1

只是编写不同组而不是Group By作为Group By不能在集合函数中使用，例如sum，max等select语句中缺少的查询语句。例如，我写了第二个查询语句

SELECT distinct c.itemID, c.itemName 
FROM item AS c 
JOIN (
SELECT b.itemID as itemid, MAX(b.item_initialPrice) AS MaxPrice FROM buyeritem AS a 
INNER JOIN item AS b ON a.item_ID = b.itemID 
GROUP BY b.itemID) as d 
ON c.itemID = d.itemid ; 

对于第二个查询

Select a.* from 
(
SELECT a.ownerID, b.sellerName, count(distinct a.ITEM_ID) as item_qty 
FROM item AS a 
INNER JOIN seller AS b ON a.ownerID = b.sellerID 
GROUP BY a.ownerID,b.sellerName 
) a 
order by item_qty DESC