SQL订单小计求和函数异常求助（Northwind库+SSMS环境）

Got it, let's fix your SQL script step by step. I can spot a couple of syntax issues that are causing the column name/syntax errors you're seeing:

1. 核心语法错误：小数格式化写法不对 #

You tried to wrap the SUM calculation and the decimal place 2 in a single parentheses, which isn't valid SQL syntax. To round the subtotal to 2 decimal places, you need to use the ROUND() function properly—wrap the entire aggregate calculation inside ROUND(), with the decimal count as the second parameter.

2. 不完整的分组子句 #

Your GROUP BY clause cuts off at Ord...—you need to explicitly include OrderID here, since it's a non-aggregated column in your SELECT clause (SQL requires all non-aggregated columns to be listed in GROUP BY).

修正后的完整脚本 #

SELECT 
    [OrderID],
    ROUND(SUM(UnitPrice * Quantity * (1 - Discount)), 2) AS [Order Subtotal]
FROM 
    [dbo].[Order Details]
GROUP BY 
    [OrderID]

可选：更精确的小数截断（避免四舍五入） #

If you want to truncate the result to 2 decimals instead of rounding it, use CAST() to convert the sum to a DECIMAL type with fixed precision:

SELECT 
    [OrderID],
    CAST(SUM(UnitPrice * Quantity * (1 - Discount)) AS DECIMAL(10, 2)) AS [Order Subtotal]
FROM 
    [dbo].[Order Details]
GROUP BY 
    [OrderID]

内容的提问来源于stack exchange，提问作者DoktorAgon