sql - 如何定义这样的计算列？

Question

我Equipment在 SQL Server 2008 中有一个像这样的表：

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 
)

我希望有一个计算列WarrantyStatus，该列将在计算时Unexpired或Expired在计算时返回，基于列ProducedDate和WarrantyPeriod.

这是错误的，但这是我想要的：

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

Answer 1

尝试：

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