SQL Server和嵌套的SELECT：...'）'附近的语法不正确？

Question

执行我的代码时出现此错误。这是什么意思？我正在使用SQL Server Management Server Express。

消息102，级别15，状态1，行7

附近有语法错误 '）'。

---

declare @start datetime 
declare @end datetime 
set @start = '2012/01/02' 
set @end = '2012/01/06' 


SELECT 
SUM(VCount) as [Total], 
vdate, 
(select COUNT(VIP) From (SELECT DISTINCT(VIP) FROM dbo.Visiter)) as [IP3] 
FROM dbo.Visiter 
where VDate between @start and @end 
GROUP BY VDate 

Answer 1

在SQL Server中，当你在FROM子句中使用派生表（子查询），你必须给派生表的别名：

SELECT 
SUM(VCount) as [Total], 
vdate, 
-- add an alias in the next line 
(select COUNT(VIP) From (SELECT DISTINCT(VIP) FROM dbo.Visiter) AS a) as [IP3] 
FROM dbo.Visiter 
where VDate between @start and @end 
GROUP BY VDate 

参考：FROM clause

Answer 2

我觉得这

(select COUNT(VIP) From (SELECT DISTINCT(VIP) FROM dbo.Visiter)) as [IP3] 

是更好地转化为

(select COUNT(DISTINCT VIP) FROM dbo.Visiter) as [IP3] 

据我所知，MySQL的，至少说Every derived table must have its own alias这样，你的子查询早该样子

(select COUNT(v) From (SELECT DISTINCT(VIP) AS v FROM dbo.Visiter) AS tmp1) as [IP3] 

但短 - 好=）