sql - 为什么 SQL Select 语句语法不正确？

Question

刚接触 SQL，我们非正式地学习了语法，不知道我错过了什么。

无法更改数据库

Select Sum('Unit Price') as TotalPrice, Count('Order ID') as NumOfDiffProds, 
Avg(Quantity) as AvgQuantity, Avg(Discount) as AvgDiscount
From [Order Details]
Where [Order ID] = 1

我收到此错误：

SELECT 语句包含拼写错误或丢失的保留字或参数名称，或者标点符号不正确

Answer 1

删除列名中的单引号

Select Sum("Unit Price") as TotalPrice, 
Count("Order ID") as NumOfDiffProds, 
Avg(Quantity) as AchQuantity, Avg(Discount) as AvgDiscount
FROM TableName;

Answer 2

我认为您正在使用MySQL。您可以使用反引号来引用带有空格的表名或列名：

Select 
    Sum(`Unit Price`) as TotalPrice, 
    Count(`Order ID`) as NumOfDiffProds, 
    Avg(`Quantity`) as AvgQuantity, 
    Avg(`Discount`) as AvgDiscount
From 
    `Order Details`
Where 
    `Order ID` = 1

一个建议：尽量避免创建名称中带有空格的数据库对象。