SQL Server觸發器遞歸在級聯刪除

Question

我有一個包含樹狀結構表

它採用的形式：

-nodeID，fkID，parentNode

（parentNode爲NULL如果它是它的父節點的根，並且它是子節點） （如果它不是根，fkID爲NULL）

fkID是一個FK，當它在另一個表中刪除時，將其刪除級聯到該表中。然而，這種級聯刪除僅引用根節點。對數據庫還有一個限制，在該數據庫中，除非首先刪除其子節點，否則無法刪除根節點。但是我無法級聯自引用約束，因爲SQL SERVER不能給我這個選項。我認爲觸發器可能是一個很好的解決方案，但是我必須首先對樹進行遞歸，並在父母面前刪除孩子。這將需要我在級聯發生之前刪除。有沒有一個好的方法來做到這一點？

我已經收到以下錯誤以下觸發

SET ANSI_NULLS ON 
GO 
SET QUOTED_IDENTIFIER ON 
GO 
CREATE TRIGGER dbo.deleteChildren 
ON dbo.faultTreeNodes 
INSTEAD OF DELETE 
AS 
BEGIN 
SET NOCOUNT ON; 
    -- Insert statemets for trigger here 
END 
GO 

錯誤：

CANNOT CREATE TRIGGER INSTEAD OF DELETE BECAUSE THIS 
TABLE HAS A FOREIGN KEY WITH A CASCADING DELETE 

預先感謝您的任何建議或幫助！

Answer 1

儘管我已經投票結束爲duplicate，但我想我會發佈一個答案，因爲在第二個想法中，重複問題的答案最終在編輯問題後變得有點令人困惑，並且最近添加的聲明

I guess you just need to drop that ON DELETE CASCADE flag from your recursive foreign key in Categories. The CASCADE flag on the foreign key from CAT_SCH should not matter

實際上是不正確的（SQL Server將產生一個錯誤上刪除，因爲cascade在一個領域將no action上的另一場衝突）。

要點保持，但：

• 您作爲on delete no action同時聲明外鍵。
• 您在「主」表上創建一個instead of delete觸發器，它將按順序刪除所需的子項，然後刪除「主」記錄本身。

例如， （SQL Fiddle）：

create table main(id int not null primary key); 

create table nodes (
    nodeID int not null primary key, 
    fkID int null foreign key references main(id), 
    parentID int null foreign key references nodes(nodeID) 
); 

create trigger dlt on main 
instead of delete 
as 
begin 

    declare @to_delete table (nodeID int not null, level int not null, primary key(level, nodeID)); 

    begin tran; 

    with cte as (
    select n.nodeID, 0 as level 
    from nodes n inner join deleted d on n.fkID = d.id 

    union all 

    select n.nodeID, level + 1 
    from nodes n inner join cte c on n.parentID = c.nodeID 
) 
    insert into @to_delete(nodeID, level) 
    select nodeID, level 
    from cte; 

    declare cur cursor 
    local 
    forward_only 
    read_only 
    for 
    select distinct level from @to_delete order by level desc; 

    open cur; 

    declare @cur_level int; 

    fetch next from cur into @cur_level; 
    while @@fetch_status = 0 
    begin 
    delete from nodes 
    from nodes n inner join @to_delete d on n.nodeID = d.nodeID 
    where d.level = @cur_level; 

    fetch next from cur into @cur_level; 
    end; 


    close cur; 
    deallocate cur; 

    delete from main from main m inner join deleted d on m.id = d.id; 

    commit tran; 
end;