Question

我有下表：

if object_id(N'dbo.Node') is null
create table dbo.Node
(
    ID bigint identity primary key,
    ParentID bigint null foreign key references Node(ID) on delete no action,
    DateCreated datetime not null,
    LastUpdated datetime not null,
    [Name] nvarchar(500) not null,
);

现在，因为SQL Server在我尝试将外键设置为级联删除时会抱怨，所以我创建了一个触发器来完成这项工作：

create trigger Node_Delete on Node for delete
as
begin
    delete from Node where ParentID in (select id from deleted)
end

现在这是一个示例数据集：

ID                   ParentID             DateCreated             LastUpdated             Name
520                  1                    2010-01-12 02:26:26.890 2010-01-12 02:26:26.890 Test 1
523                  520                  2010-01-12 02:32:44.777 2010-01-12 02:32:44.777 Test 2

现在让我们运行这一点SQL：

delete from Node where ID=520

节点应与子节点一起删除。那么为什么我会收到此错误？

Msg 547, Level 16, State 0, Line 1
The DELETE statement conflicted with the SAME TABLE REFERENCE constraint "FK__Node__ParentID__117F9D94". The conflict occurred in database "mydb", table "dbo.Node", column 'ParentID'.
The statement has been terminated.

Answer 1

外键阻止初始删除，触发器永远不会触发。尝试使用INSTEAD OF触发器从最远的死者中删除。

为什么我的触发器不会触发？

1 个答案: