mysql - 在第 4 列中添加 3 列(具有 avg() 值)

Question

我有一个有 3 列的表；时间检索、时间处理和时间渲染。所有这 3 列都显示平均值。现在，我想添加这些平均值并将其显示在名为“AvgTotalTime”的第四列中。

我的查询现在看起来是这样的:

Select 
avg(a.TimeRetrieval) as "Retrieval time",
avg(a.TimeProcessing) as "Processing time",
avg(a.TimeRendering) as "Rendering Time",
(avg(a.TimeRetrieval)+avg(a.TimeProcessing)+avg(a.TimeRendering)) AS "AvgTotalTime"
from TimeLog a

我知道添加 3 列有问题，但无法弄清楚执行此操作的 corerct 语法。

Answer 1

试试这个

SELECT [Retrieval time],
       [Processing time],
       [Rendering Time],
       [Retrieval time]+[Processing time]+[Rendering Time] AS "AvgTotalTime"
FROM 
( 
     Select 
     avg(a.TimeRetrieval) as "Retrieval time",
     avg(a.TimeProcessing) as "Processing time",
     avg(a.TimeRendering) as "Rendering Time"
     from TimeLog a
 )M