Question

我对TSQL中的触发器有疑问。

我们说我有3张桌子：

Companies
---------
Id

Employees
---------
Id
CompanyId

Tasks
-----
EmployeeId

现在我为前2个表格Companies和Employees创建了2个触发器：

CREATE TRIGGER DeleteCompany
    ON [dbo].[Companies]
    INSTEAD OF DELETE
AS
    DELETE FROM [dbo].[Employees]
    WHERE CompanyId IN (SELECT Id FROM deleted)     
GO

CREATE TRIGGER DeleteEmployee
    ON [dbo].[Employees]
    INSTEAD OF DELETE
AS
    DELETE FROM [dbo].[Tasks]
    WHERE EmployeeId IN (SELECT Id FROM deleted)        
GO

到目前为止一切顺利。现在，如果我删除公司，将执行触发器DeleteCompany并删除映射的Employees。我的问题是，这会导致触发器DeleteEmployee执行吗？因为我试图基本上这样做，但只执行第一个触发器（DeleteCompany）。

Answer 1

好的，我发现了问题。我对INSTEAD OF实际做了什么感到有些困惑。事实证明，它完全取代了DELETE，因此在删除它之后我必须删除它的实际记录，如下所示：

CREATE TRIGGER DeleteCompany
    ON [dbo].[Companies]
    INSTEAD OF DELETE
AS
    DELETE FROM [dbo].[Employees]
    WHERE CompanyId IN (SELECT Id FROM deleted)  

    DELETE [dbo].[Companies] WHERE [dbo].[Companies].Id IN (SELECT Id FROM deleted)   
GO

CREATE TRIGGER DeleteEmployee
    ON [dbo].[Employees]
    INSTEAD OF DELETE
AS
    DELETE FROM [dbo].[Tasks]
    WHERE EmployeeId IN (SELECT Id FROM deleted) 

    DELETE [dbo].[Employees] WHERE [dbo].[Employees].Id IN (SELECT Id FROM deleted)            
GO

这样做可以实现所需的级联删除效果。

这是让我意识到这一点的帖子：Link

Do触发器会导致其他触发器执行吗？

1 个答案: