SQL分组依据错误-“；不是按表达式分组；

我的SQL查询似乎有问题，这让我很恼火。我似乎无法让大家一起工作。我不断得到以下错误：

00979. 00000 -  "not a GROUP BY expression"

我的查询：

SELECT customers.customer_first_name, customers.customer_last_name, orders.customer_numb, books.author_name, books.title
FROM customers
LEFT OUTER JOIN orders ON (orders.customer_numb = customers.customer_numb)
LEFT OUTER JOIN order_lines ON (order_lines.order_numb = orders.order_numb)
LEFT OUTER JOIN books ON (books.isbn = order_lines.isbn)
WHERE (customers.customer_numb = 6)
GROUP BY (books.title)

数据库架构：

客户：

SELECT customers.customer_first_name, customers.customer_last_name, orders.customer_numb, books.author_name, books.title
FROM customers
LEFT OUTER JOIN orders ON (orders.customer_numb = customers.customer_numb)
LEFT OUTER JOIN order_lines ON (order_lines.order_numb = orders.order_numb)
LEFT OUTER JOIN books ON (books.isbn = order_lines.isbn)
WHERE (customers.customer_numb = 6)
GROUP BY (books.title)

订单行和订单：

SELECT customers.customer_first_name, customers.customer_last_name, orders.customer_numb, books.author_name, books.title
FROM customers
LEFT OUTER JOIN orders ON (orders.customer_numb = customers.customer_numb)
LEFT OUTER JOIN order_lines ON (order_lines.order_numb = orders.order_numb)
LEFT OUTER JOIN books ON (books.isbn = order_lines.isbn)
WHERE (customers.customer_numb = 6)
GROUP BY (books.title)

我正在努力实现的目标： 我试图按书名分组，这样就不会显示重复的书名

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如果我错过了什么，我向你道歉，谢谢。

你还不明白什么？select语句包含许多不在

group by

子句中的列。试试这个：

SELECT customers.customer_first_name, customers.customer_last_name, orders.customer_numb, books.author_name, books.title 
FROM customers 
LEFT OUTER JOIN orders ON (orders.customer_numb = customers.customer_numb) 
LEFT OUTER JOIN order_lines ON (order_lines.order_numb = orders.order_numb) 
LEFT OUTER JOIN books ON (books.isbn = order_lines.isbn) 
WHERE (customers.customer_numb = 6) 
GROUP BY customers.customer_first_name, customers.customer_last_name, orders.customer_numb, books.author_name, books.title  

由于您没有聚合任何内容，因此可以省去

group by

，只需在

select

子句中使用

distinct

：

select distinct  customers.customer_first_name, customers.customer_last_name, orders.customer_numb, books.author_name, books.title 

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也许可以使用DISTINCT

听起来你想要的是一份客户名单和他们购买的不同书籍。我会像这样重写查询，它应该满足您的要求：

select c.customer_first_name ,
       c.customer_last_name  ,
       c.customer_numb       ,
       b.author_name         ,
       b.title               
from customers c
left join ( select distinct
                   o.customer_numb ,
                   ol.isbn         
            from      orders      o
            left join order_lines ol on ol.order_number = orders.order_numb
          ) cb on cb.customer_numb = c.customer_numb
join books b on b.isbn = cb.isbn
where c.customer_numb = 6

如果要计算他们购买的每个标题的数量，请将from子句中的派生表（也称为内联视图或虚拟表）更改为使用

GROUPBY

，而不是

select distinct

，并将适当的聚合函数添加到结果集中

这里是原始查询南下的地方：结果集中的每一列都必须是

• group by

  子句中的列或表达式
• 文字，或
• 聚合函数

虽然这里有一些例外（例如，您可以有一个仅依赖于分组列和聚合函数的表达式），虽然SQL标准假定允许其他列，但大多数实现不允许

考虑这样一个查询，其中客户和订单之间存在一对多关系，单个订单可能被发送到一个地址或另一个地址

select c.customer_id , o.shipping_address , orders = count(*)
from customer c
join order    o on o.customer_id
group by c.customer_id

在此上下文中，

o.shipping\u address

的语义是什么？您已按客户id对订单进行分组，并将整个组折叠为一行

customer\u id

很容易，因为这是分组标准：根据定义，整个组共享相同的值<代码>计数（*）也很简单，因为它只是组中的行计数

“shipping_address”是一个问题：该组可能有多个shipping address值，但聚合组只能返回一个值。第一？最后？还有别的吗

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SQL Server过去有一个非常不标准的实现，允许这种奇怪的东西。在本例中，它所做的是将组聚合为一行，然后跨组中的所有行将聚合的行连接起来。不完全是直觉行为。

你的答案非常有效。一个问题，只有当我选择与select中相同的值时，group by才会起作用吗？在标准SQL和大多数数据库引擎中，不属于聚合函数的所有列（如SUM、AVG、MIN、MAX）都需要位于

group by

子句中。但在查询中选择的任何列上都没有Agg函数。那为什么要用

分组？我不明白。@Annjawn。在这种情况下，
groupby
与
distinct
具有相同的效果。是的，我认为他想使用
disect
<如果在所选的任何列中使用了聚合函数，则使用“代码>分组依据”

。检查select语句中的所有列是否都在group by中…查询中没有聚合函数。那为什么要用

分组？