SQL：刪除所有嵌套自參照記錄

Question

這是一個表的結構：Id Name ParentId

ParentId是一個外鍵，主列Id。現在讓我們說我有這樣幾行：（只顯示ParentId來自行）

 01 
/ \ 
    5  2 
     /\ 
     3 4 

我已經安裝InsteadOfDelete觸發，如下圖所示：

CREATE TRIGGER [dbo].[tr_tb] ON [dbo].[Some_tb] 
    INSTEAD OF DELETE 
AS 
    /*Delete from another table*/ 
    DELETE FROM SomeOther_tb WHERE OtherId IN(SELECT Id FROM deleted); 

    /*Delete childs from this table*/ 
    DELETE FROM Some_tb WHERE ParentId IN(SELECT Id FROM deleted); 

    /*Delete from this table*/ 
    DELETE FROM Some_tb WHERE Id IN(SELECT Id FROM deleted); 

當Id = 01（記錄查詢以上孩子的代表性）被刪除。只有直接孩子（Id=5,2）被刪除，留下子孩子記錄（Id = 3,4）。

我假設InsteadOfTrigger功能不會觸發子女（Id=5,2）。

如何解決此問題，以便刪除所有嵌套的子節點？

Answer 1

DECLARE @DELETED TABLE(
     Id BIGINT 
    ); 


WITH LoopCTE AS (
    SELECT Id, ParentId,0 AS steps 
    FROM dbo.Some_tb 
    WHERE Id IN (SELECT Id FROM deleted) 

    UNION ALL 

    SELECT mgr.Id, mgr.ParentId, parent.steps +1 AS steps 
    FROM LoopCTE AS parent 
    INNER JOIN dbo.Some_tb AS mgr 
     ON parent.Id = mgr.ParentId 
) 
INSERT INTO @DELETED SELECT Id FROM LoopCTE AS u; 

/*Delete from another table*/ 
DELETE FROM SomeOther_tb WHERE OtherId IN(SELECT Id FROM @DELETED); 


/*Delete childs from this table*/ <-- No longer required 
/*DELETE FROM Some_tb WHERE ParentId IN(SELECT Id FROM @DELETED);*/ 

/*Delete from this table*/ 
DELETE FROM Some_tb WHERE Id IN(SELECT Id FROM @DELETED); 

Answer 2

CREATE TRIGGER [dbo].[tr_tb] ON [dbo].[Some_tb] 
    INSTEAD OF DELETE 
AS 
    DECLARE @DELETED TABLE(
     ID BIGINT 
    ) 

    INSERT INTO @DELETED 
     SELECT Id FROM deleted 

    --could use a CTE here as well for better performance 
    WHILE @@ROWCOUNT>0 
     BEGIN 
      INSERT INTO @DELETED 
       SELECT Id 
       FROM Some_tb t 
       inner join @DELETED d on d.parentid=t.id 
     END 

    /*Delete from another table*/ 
    DELETE FROM SomeOther_tb WHERE OtherId IN(SELECT Id FROM @DELETED); 

    /*Delete childs from this table*/ 
    DELETE FROM Some_tb WHERE ParentId IN(
     SELECT Id FROM @DELETED WHERE ID NOT IN (SELECT ID FROM DELETED) 
    ); 

    /*Delete from this table*/ 
    DELETE FROM Some_tb WHERE Id IN(SELECT Id FROM DELETED); 

Answer 3

MS SQL Server 2008支持通用表表達式（CTE），這是偉大的分層數據。 CTE也可能存在觸發器。

CREATE TRIGGER [dbo].[tr_tb] ON [dbo].[Some_tb] 
    INSTEAD OF DELETE 
AS 
    /*Delete from another table*/ 
    ;with tbl as (--this is CTE 
     --anchor query (top level) 
     select t.id, t.parentid 
     from someOther_tb t 
     inner join deleted d on d.id = t.parentid 
     union all 
     --recursive query 
     select t.id, t.parentid 
     from someOther_tb t 
     inner join tbl on tbl.id=t.parentid 
    ) 
    delete someOther_tb 
    where id in (select id from tbl)   

    --Now it is safe to delete from main table 
    DELETE FROM Some_tb WHERE Id IN(SELECT Id FROM deleted)