sql - 查找返回多行的计数(*)的平均值

Question

您好，我正在尝试计算结果集的平均值，但我无法这样做选择 count(*) 的查询返回 1 月 1 日至 31 日之间每一天的调用计数，因此返回了近 20 行。我应如何计算结果的平均值，然后将该值分配给变量，如 SET @abc =(下面的查询)。我正在使用 sql server 2005。

SELECT avg(Calls) AS average 
FROM
(
     SELECT COUNT(*) Calls      
     FROM abc 
     WHERE CallDate  BETWEEN '20120101'  AND '20120131' 
     AND datepart(Hh,TranscribeDateTime) = '07' 
     AND datepart(Mi,TranscribeDateTime) BETWEEN '00' AND '59'  
     AND AppID = 123 AND Status ='T' 
     GROUP BY calldate
)

如果我的方法有误，请提出一个。谢谢你

Answer 1

看起来你只是缺少派生表的表别名(SQL Server 中需要)和赋值语句(如果你将它分配给 AS average 列，你也不能别名一个变量)

DECLARE @ABC INT;

SELECT @ABC = AVG(Calls)
FROM
(
     SELECT COUNT(*) Calls      
     FROM abc 
     WHERE CallDate  BETWEEN '20120101'  AND '20120131' 
     AND datepart(Hh,TranscribeDateTime) = '07' 
     AND datepart(Mi,TranscribeDateTime) BETWEEN '00' AND '59'  
     AND AppID = 123 AND Status ='T' 
     GROUP BY calldate
) T  /* <-- Alias here */