Sql 如何在Select语句中获取count返回的值

我有以下sql查询：

Select Invoices.ID, count(*) invoices
From
   Customers.ID F
   Inner join Invoices p
   On P.ID=F.ID and f.ID = 1
group by p.ID
GO

我想做的是在按p.ID分组之后的if语句中使用count（）发票，但是我似乎无法找到获得该值的方法。我知道我可以通过删除GROUPBY子句来进行行计数，但我更希望得到count（）值

Select Invoices.ID, count(*) invoices
From
   Customers.ID F
   Inner join Invoices p
   On P.ID=F.ID and f.ID = 1
group by p.ID
if ("value from count(*) invoices) = 0
  do some stuff here
else
  do some other stuff here
GO

谢谢你的帮助。

---

Shimon将值放入变量中。大概是这样的：

declare @invoice_id int;
declare @myCount int;

Select @invoice_id = Invoices.ID, @myCount = count(*)
From
   Customers.ID F
   Inner join Invoices p
   On P.ID=F.ID and f.ID = 1
group by p.ID
if (@myCount) = 0
  do some stuff here
else
  do some other stuff here
GO

---

查询中的用例语句

Select Invoices.ID, 
Case When count(*)=0 
 then "do something" 
 else "do something" end AS invoices
From
   Customers.ID F
   Inner join Invoices p
   On P.ID=F.ID and f.ID = 1
group by p.ID
GO

---

为变量赋值的select语句不得与数据检索结合使用operations@Shimon我忘记了发票id。请尝试我的更新答案。