Access SQL查询返回计数字段的错误值

我正在尝试进行一个

SQL

查询，得到的是客户的姓名加上一列

c

，这是

计数
连接到
客户的转介的行数。[客户ID]=转介。[转介自]
和
转介。[使用我们的服务]=True

第二列为of
c2
，这是连接到
客户的转介的行数。[客户ID]=转介。[转介自]
和
转介。[有效转介]=True

此查询工作正常，但在
c2
列中返回了错误的数字。它应该是1时返回2

SELECT 
Customers.[Customer ID], Customers.[First Name], Customers.[Last Name], Count(r.[Valid Referral]) AS c, Count(rr.[Used Our Service]) AS c2
FROM (Customers 
INNER JOIN Referrals r ON Customers.[Customer ID] = r.[Referred From] AND (r.[Valid Referral])=True)
INNER JOIN Referrals rr ON Customers.[Customer ID] = rr.[Referred From] AND (rr.[Used Our Service])=True
WHERE (r.[Valid Referral])=True
GROUP BY Customers.[Customer ID], Customers.[First Name], Customers.[Last Name]

客户表：


转介表格：


结果表：

我建议您将
SUM
与
Iif
一起使用，而不是两次加入同一个表，如下所示：

SELECT 
Customers.[Customer ID], 
Customers.[First Name], 
Customers.[Last Name], 
SUM(Iif(r.[Valid Referral] = True, 1, 0)) AS c, 
Sum(Iif(r.[Used Our Service] = True, 1, 0)) AS c2
FROM Customers 
INNER JOIN Referrals r ON Customers.[Customer ID] = r.[Referred From] 
WHERE (r.[Valid Referral])=True
GROUP BY Customers.[Customer ID], Customers.[First Name], Customers.[Last Name]