我对 Northwind 数据库 Products Table 运行了一个查询，如下所示
select * from Northwind.dbo.Products GROUP BY CategoryID 并且遇到了错误。我相信您也会遇到同样的错误。那么我需要执行的正确语句是什么来根据类别 ID 对所有产品进行分组。
编辑：这确实有助于理解很多
http://weblogs.sqlteam.com/jeffs/archive/2007/07/20/but-why-must-that-column-be-contained-in-an-aggregate.aspx
I ran a query against Northwind database Products Table like below
select * from Northwind.dbo.Products GROUP BY CategoryID and i was hit with a error. I am sure you will also be hit by same error. So what is the correct statement that i need to execute to group all products with respect to their category id's.
edit: this like really helped understand a lot
http://weblogs.sqlteam.com/jeffs/archive/2007/07/20/but-why-must-that-column-be-contained-in-an-aggregate.aspx
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您需要使用聚合函数，然后按任何非聚合列进行分组。
我建议阅读GROUP BY。
You need to use an Aggregate function and then group by any non-aggregated columns.
I recommend reading up on GROUP BY.
如果您在查询中使用
GROUP BY，则SELECT语句中的所有项目都必须包含在聚合函数中，例如Sum()< /code> 或Count()，否则它们也需要包含在GROUP BY子句中。由于您使用的是
SELECT *，因此这相当于列出SELECT中的所有列。因此，要么将它们全部列在
GROUP BY中，尽可能对其余部分使用聚合函数，或者仅选择CategoryID。If you're using
GROUP BYin a query, all items in yourSELECTstatement must either be contained as part of an aggregate function, e.g.Sum()orCount(), else they will also need to be included in theGROUP BYclause.Because you are using
SELECT *, this is equivalent to listing ALL columns in yourSELECT.Therefore, either list them all in the
GROUP BYtoo, use aggregating functions for the rest where possible, or only select theCategoryID.