Question

我有一个可以为空的FK字段的表。我把它做成了nullablle以避免更换装载机。

为了实现（广告商）* 1（货币），我写了一个简单的触发器：

ALTER TRIGGER InsertedAdvertisersDefaultCurrency
ON dbo.Advertisers
FOR INSERT
AS
    UPDATE Advertisers
    SET Currency_Id=(SELECT TOP 1 Id FROM Currencies WHERE Name='USD')
    WHERE Currency_Id=NULL

我的问题基本上是关于我如何在每个插页上检查整个表的空行。

我觉得我应该使用插入的表（？）

这是表格：

CREATE TABLE [dbo].[Advertisers](
    [Id] [int] IDENTITY(1,1) NOT NULL,
    [Name] [nvarchar](max) NOT NULL,
    [Currency_Id] [int] NULL,
 CONSTRAINT [PK_Advertisers] PRIMARY KEY CLUSTERED 
(
    [Id] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]
GO
ALTER TABLE [dbo].[Advertisers]  WITH CHECK ADD  CONSTRAINT [FK_CurrencyAdvertiser1] FOREIGN KEY([Currency_Id])
REFERENCES [dbo].[Currencies] ([Id])
GO
ALTER TABLE [dbo].[Advertisers] CHECK CONSTRAINT [FK_CurrencyAdvertiser1]
GO

Answer 1

是的，您应该只更新插入的记录：

UPDATE Advertisers
SET Currency_Id=(SELECT TOP 1 Id FROM Currencies WHERE Name='USD')
WHERE Id in (select Id from inserted)

或者您可以在该字段中使用默认值

ALTER TABLE [dbo].[Advertisers] ADD  CONSTRAINT [DF_Advertisers_Currency_Id]  DEFAULT ((101)) FOR [Currency_Id]
GO

其中101是美元ID

我应该在此触发器中使用inserted表来设置可为空的外键的默认值吗？

1 个答案: