SQL：删除所有嵌套自参照记录

Question

这是一个表的结构：Id Name ParentId

ParentId是一个外键，主列Id。现在让我们说我有这样几行：（只显示ParentId来自行）

 01 
/ \ 
    5  2 
     /\ 
     3 4 

我已经安装InsteadOfDelete触发，如下图所示：

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); 

当Id = 01（记录查询以上孩子的代表性）被删除。只有直接孩子（Id=5,2）被删除，留下子孩子记录（Id = 3,4）。

我假设InsteadOfTrigger功能不会触发子女（Id=5,2）。

如何解决此问题，以便删除所有嵌套的子节点？

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支持通用表表达式（CTE），这是伟大的分层数据。 CTE也可能存在触发器。

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)