SQL幫助：查詢問題

Question

我不斷遇到問題。我需要得到的是前3個AVG率最高的國家。

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

這應該工作：

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

的問題是單引號AverageRate。只對字符串和日期常量使用單引號。你不需要他們在這裏，所以只是將其刪除：

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; 

您查詢沒有下令由你是一個恆定值，字符串「AverageRate」訂貨。如果您需要轉義標識符，請使用雙引號或方括號（Sybase和SQL Server特定）。