MS-Access SQL语法错误中的子查询

Question

晚上好。

我正在尝试创建一个查询，对每个产品购买量与平均值进行比较。 购买次数以获得平均购买金额。

这包括三个表：

1. 顾客
2. 发票
3. 线

我这样写：

SELECT CUSTOMER.CUS_CODE, CUS_FNAME+" "+CUS_LNAME AS Name, CUSTOMER.CUS_BALANCE,    
Sum([LINE]![LINE_NUMBER]*[LINE]![LINE_PRICE]) AS Total_purchases,  
Count(INVOICE.INV_NUMBER) AS Number_of_purchases, 

(
SELECT [Sum([LINE]![LINE_NUMBER]*[LINE]![LINE_PRICE]) /   
[Count(INVOICE.INV_NUMBER)]
FROM INVOICE, LINE
WHERE INVOICE.INV_NUMBER = LINE.INV_NUMBER
) AS Average_purchase_amount

FROM CUSTOMER, INVOICE, LINE
WHERE CUSTOMER.CUS_CODE = INVOICE.CUS_CODE AND INVOICE.INV_NUMBER = LINE.INV_NUMBER 
GROUP BY CUSTOMER.CUS_CODE, CUS_FNAME+" "+CUS_LNAME, CUSTOMER.CUS_BALANCE;

---

在第二个SELECT时出现错误。 我不知道为什么。 我觉得我缺少一些非常简单的东西。

实际错误为：

• “查询表达式'（SELECT [Sum（[LINE]！[LINE_NUMBER] * [LINE]！[LINE_PRICE]）/ [Count（INVOICE.INV_NUMBER）]的语法错误。'”

根据错误，我认为表达式中的某处没有排列整齐，但是我想我对所发生的事情还不了解，确切地知道它到底是什么。

Answer 1

有不平衡的括号。 每个括号都应放在方括号中或放在整个方程中：

SELECT [Sum([LINE]![LINE_NUMBER]*[LINE]![LINE_PRICE])] / [Count(INVOICE.INV_NUMBER)]

- 要么 -

SELECT [Sum([LINE]![LINE_NUMBER]*[LINE]![LINE_PRICE]) /  Count(INVOICE.INV_NUMBER)]

尝试加入表格。 像这样：

FROM INVOICE
    INNER JOIN CUSTOMER ON CUSTOMER.CUS_CODE = INVOICE.CUS_CODE
    INNER JOIN LINE ON LINE.INV_NUMBER =INVOICE.INV_NUMBER