group by by desc

Question

select aaa.BookId from 
(SELECT  TOP (100) PERCENT Id, BookId,CreatedOnUtc 
         FROM   dbo.Chapter AS c 
         ORDER BY CreatedOnUtc desc    
         ) as aaa 
group by aaa.BookId 

ORDER BY CreatedOnUtc desc怎麼樣對結果沒有任何影響。

我想要得到的結果是這樣

BookId (with desc createdonUtc) 
3 
4 
1 
... 

更新：我去與這個

select BookId, Max(CreatedOnUtc) 
from Chapter 
group by BookId 
order by Max(CreatedOnUtc) desc 

Answer 1

的ORDER BY是僅供子查詢。您的外部查詢沒有order by子句，因此結果可以按任意順序排列。

其他的事情：

• 爲什麼TOP 100 PERCENT？
• 爲什麼SELECT BookId和GROUP BY BookId但沒有聚合列？也許你只想要SELECT DISTINCT？

此外，你想達到什麼可能是不可能的。如果您的表格中有重複的BookId：

ID BookId CreatedOnUtc 
1 1  1 
2 2  2 
3 1  3 

您的結果應該以何種順序排列？ 1 2或2 1？