如何定義像這樣的計算列？

Question

我有一個Equipment表中的SQL Server 2008是這樣的：

CREATE TABLE [dbo].[Equipment](
[EquipmentID] [nchar](10) NOT NULL, 
[EquipmentName] [nchar](50) NOT NULL, 
[ProducedDate] [date] NOT NULL, 
[WarrantyPeriod] [int] NOT NULL, 
[SerialNumber] [nchar](20) NOT NULL, 
[BrandID] [tinyint] NOT NULL, 
CONSTRAINT [PK_Equipment] PRIMARY KEY CLUSTERED 
) 

我想有一個計算列WarrantyStatus這將返回Unexpired或計算時，基於列ProducedDate和WarrantyPeriodExpired。

這是不對的，但它是什麼，我想：

ALTER TABLE [dbo].[Equipment] 
ADD [WarrantyStatus] AS IIF(DATEDIFF(MONTH, [ProducedDate], GETDATE()) < [WarrantyPeriod], "Unexpired", "Expired") 

Answer 1

嘗試：

ALTER TABLE [dbo].[Equipment] 
ADD [WarrantyStatus] AS 
case when DATEDIFF(MONTH, [ProducedDate], GETDATE()) < [WarrantyPeriod] 
then 'Unexpired' 
else 'Expired' 
end