sql – 为什么将AVG(intger_column)转换为DECIMAL至少返回六位小

发布时间：2020-12-12 08:52:23 所属栏目：MsSql教程来源：网络整理

导读：考虑这个查询： WITH Scores (score) AS ( SELECT CAST(score AS INTEGER) FROM ( VALUES (0),(10),(10) ) AS Scores (score) )SELECT AVG(CAST(score AS DECIMAL(19,8))) AS precision_eight,AVG(CAST(score AS DECIMAL(19,7))) AS precision_seven,6))) AS

考虑这个查询：

WITH Scores (score)
     AS
     (
      SELECT CAST(score AS INTEGER)
        FROM (
              VALUES (0),(10),(10)
             ) AS Scores (score)
     )
SELECT AVG(CAST(score AS DECIMAL(19,8))) AS precision_eight,AVG(CAST(score AS DECIMAL(19,7))) AS precision_seven,6))) AS precision_six,5))) AS precision_five,4))) AS precision_four
  FROM Scores;

结果：

precision_eight | precision_seven | precision_six | precision_five | precision_four 
     6.66666666 |       6.6666666 |      6.666666 |       6.666666 |       6.666666

为什么我总是得到至少六位小数？这是记录在案的行为？

(我正在运行SQL Server 2008)

解决方法

小数的AVG始终返回“十进制(38,s)除以十进制(10,0)”数据类型( see here)

您必须将AVG结果转换为所需的精度.

（编辑：李大同）

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