SQL帮助：查询问题

Question

我不断遇到问题。我需要得到的是前3个AVG率最高的国家。

SELECT TOP 3 
    Country, AVG(AverageRate) AS 'AverageRate' 
FROM 
    dbo.CountryOrders 
WHERE 
    OrderDate BETWEEN '2011-01-01' AND '2011-12-31' 
GROUP BY 
    Country 
ORDER BY 
    'AverageRate' DESC; 
GO 

Answer 1

这应该工作：

SELECT TOP 3 Country, AVG(AverageRate) AS 'AverageRate' 
FROM dbo.CountryOrders 
WHERE OrderDate BETWEEN '2011-01-01' AND '2011-12-31' 
GROUP BY Country 
ORDER BY AVG(AverageRate) DESC; 
GO 

Answer 2

的问题是单引号AverageRate。只对字符串和日期常量使用单引号。你不需要他们在这里，所以只是将其删除：

SELECT TOP 3 Country, AVG(AverageRate) AS AverageRate 
FROM dbo.CountryOrders 
WHERE OrderDate BETWEEN '2011-01-01' AND '2011-12-31' 
GROUP BY Country 
ORDER BY AverageRate DESC; 

您查询没有下令由你是一个恒定值，字符串“AverageRate”订货。如果您需要转义标识符，请使用双引号或方括号（Sybase和SQL Server特定）。