Question

嗨，有人可以帮我解决这个问题。我花了很多年时间试图弄清楚出了什么问题，但没有运气

表格

发布商（publisherName，location，noOftitles）
作者（名称，位置）
书（标题，ISBN，成本，AUTHORNAME，PUBLISHERNAME）

问题

编写一个SQL命令，以显示每个拥有多个作者的发布者，发布者的名称，发布者的位置以及发布商销售的图书的平均成本。

代码：

SELECT Book.publishername, location, avg(cost)
FROM   Publisher
,      Book
WHERE  Publisher.publisherName = Book.publisherName
GROUP 
BY     publisherName
HAVING COUNT (DISTINCT authorname) >1

错误

ORA-00918：列模糊定义

正确答案：

SELECT Publisher.publisherName, Publisher.location, avg(cost)
FROM Publisher, Book
WHERE Publisher.publisherName = Book.publisherName
GROUP BY Publisher.PublisherName, Publisher.Location
HAVING COUNT (DISTINCT authorname) >1;

Answer 1

您的选择中有不明确的列名称。 select语句中的location可以来自Publisher表或Author表，GROUP BY中的publisherName可以来自Publisher或Book。您需要明确指定您希望这些值来自哪些表。

SELECT Book.publishername, Publisher.location, avg(cost)
FROM Publisher, Book
WHERE Publisher.publisherName =Book.publisherName
GROUP BY publisher.publisherName
HAVING COUNT (DISTINCT authorname) >1;

编辑：关于您的评论，您的选择中有一列不在Group By中，而不是聚合函数（例如SUM，AVG等）。您需要在GROUP BY中包含location：

SELECT Book.publishername, Publisher.location, avg(cost)
FROM Publisher, Book
WHERE Publisher.publisherName =Book.publisherName
GROUP BY publisher.publisherName, Publisher.location
HAVING COUNT (DISTINCT authorname) >1;

Answer 2

不应该是GROUP BY Book.publisherName吗？

Answer 3

位置在两个表中。您必须使用Table.Column：

来定义它

Publisher.location

Answer 4

你的小组应该阅读 GROUP BY Book.publishername

Answer 5

答案确实解释了发生了什么。这是您的查询：

SELECT Book.publishername, location, avg(cost)
FROM Publisher, Book
WHERE Publisher.publisherName =Book.publisherName
GROUP BY publisherName
---------^
HAVING COUNT (DISTINCT authorname) >1;

Oracle不知道列的来源。它可以来自任何一个表。因此，使用表别名为所有列添加前缀。此外，使用正确的连接语法，而不是隐式连接。这是您查询的更好版本：

SELECT b.publishername, p.location, avg(b.cost)
FROM Publisher p join
     Book b
     on p.publisherName = b.publisherName
GROUP BY b.publisherName
HAVING COUNT(DISTINCT b.authorname) > 1;

我猜这些列来自哪些表。

SQL多表查询

5 个答案: