Question

这很好用：

SELECT TOP 100 ExecutionTime 
FROM [Brokermate_CONFIG].[dbo].[QueryLog] 
ORDER BY ExecutedOn DESC

但是试图获得平均值会给我一个错误

SELECT AVG(executiontime) 
FROM
    (SELECT TOP 100 ExecutionTime 
     FROM [Brokermate_CONFIG].[dbo].[QueryLog] 
     ORDER BY ExecutedOn DESC
    )

错误：

＆＃39;）附近的语法错误。
。

正确的语法是什么？

由于

Answer 1

您错过了alias子查询的名称

尝试下面

SELECT AVG(executiontime) 
FROM
 (SELECT TOP 100 ExecutionTime 
  FROM [Brokermate_CONFIG].[dbo].[QueryLog]   
  ORDER BY ExecutedOn DESC
 ) A -- You need to have alias name here

Answer 2

为子查询添加别名：

SELECT AVG(sub.executiontime) AS average_execution_time
FROM (SELECT TOP 100 ExecutionTime 
      FROM [Brokermate_CONFIG].[dbo].[QueryLog] 
      ORDER BY ExecutedOn DESC) AS sub

从内部查询中获取聚合值

2 个答案: