在SQL中创建计算字段 [英] Creating calculated fields in sql

问题描述

这似乎很初级，但是我找不到一个与之匹配的简洁示例.

This will seem rudimentary but I can't find a concise example online that matches up.

我有三个领域； m1，m2和m3.我需要创建一个列或字段，这是它们三个的平均值.计算的字段将标题为就业".下面的代码就足够了吗?

I have three fields; m1, m2, and m3. I need to create a column or field that is the average of them three. The calculated field would be titled employment. Would the following code be suffice?

ALTER TABLE dbo.tablename ADD Employment AS Select ((m1+m2+m3)/3)

样本数据

m1   20    20    30
m2   15    17    25
m3   60    77    13

期望的结果.

Name        m1    m2    m3   Employment
Auto body    20    20    30     23
Auto Parts   15    17    25     19
Auto Sales   60    77    13     50

推荐答案

您非常亲密，它称为Computed Column

https://technet.microsoft. com/en-us/library/ms191250(v = sql.105).aspx

ALTER TABLE dbo.tablename ADD Employment AS ((m1+m2+m3)/3)

更新:

如果您想强制计算列的数据类型，则可以执行以下操作

If you would like to force data type for a computed column, you could do the following

ALTER TABLE dbo.tablename ADD Employment AS CAST((m1+m2+m3)/3 AS Numeric (9,0))

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