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

sql-server-2008 sql-server sql

6

onedaywhen · 技术社区 · 15 年前

请考虑以下查询:

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, 
       AVG(CAST(score AS DECIMAL(19, 6))) AS precision_six, 
       AVG(CAST(score AS DECIMAL(19, 5))) AS precision_five, 
       AVG(CAST(score AS DECIMAL(19, 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

(我正在运行SQL Server 2008)

2 回复 | 直到 15 年前

1

9

Carvellis 15 年前

decimal的AVG总是返回“decimal(38,s)除以decimal(10,0)”数据类型( see here )

你必须将平均结果转换为所需的精度。

2

Community Mohan Dere 9 年前

我正要发布类似于 Jappie's answer

declare @a int
set @a = 0
declare @b int
set @b = 10
declare @c int
set @c = 10

declare @n decimal(10,0)
set @n = 3

select cast((@a+@b+@c) as decimal(38,4))/@n