MS SQL“删除级联"多个外键指向同一张表?-数据库问题

MS SQL quot;ON DELETE CASCADEquot; multiple foreign keys pointing to the same table?(MS SQL“删除级联多个外键指向同一张表?)

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问题描述

我有一个问题，我需要对指向同一个表的多个外键进行级联..

[洞察]|身份证 |标题 ||1 |巨蟒 ||2 |斯帕马洛特 |[BroaderInsights_Insights]|更广泛的见解_id |洞察ID ||1 |2 |

基本上，当洞察表中的一条或两条记录被删除时，我也需要删除关系..

我试过了:

 CREATE TABLE broad_insights_insights(id INT NOT NULL IDENTITY(1,1),broad_insight_id INT NOT NULL REFERENCESInsights(id) ON DELETE CASCADE,insight_id INT NOT NULL REFERENCESInsights(id) ON DELETE CASCADE,主键(id))去

<块引用>

这会导致警告说级联可能导致循环或多级联路径"

所以我尝试将级联添加到insight_id，结果是:

<块引用>

DELETE 语句与 REFERENCE 约束冲突

有什么想法吗?

谢谢

丹尼尔

解决方案

您必须将此作为 INSTEAD OF 删除触发器来实现洞察力，才能使其正常工作.比如:

创建触发器 T_Insights_D洞察力而不是删除作为设置不计数从更广泛的见解中删除其中insight_id in(从已删除中选择ID)或broad_insight_id in(从已删除中选择 ID)从 ID 所在的 Insights 中删除(从已删除中选择 ID)

<小时>

经常使用级联删除和大量外键，您需要花时间制定级联"顺序，以便在树"顶部发生的删除成功级联到引用表.但在这种情况下这是不可能的.

I have a problem where i need a cascade on multiple foreign keys pointing to the same table..

[Insights]
| ID | Title        |
| 1  | Monty Python |
| 2  | Spamalot     | 

[BroaderInsights_Insights]
| broaderinsight_id | insight_id |
| 1                 | 2          |

Basically when either record one or two in the insights table is deleted i need the relationship to also be deleted..

I've tried this:

 CREATE TABLE broader_insights_insights(id INT NOT NULL IDENTITY(1,1),
   broader_insight_id INT NOT NULL REFERENCES insights(id) ON DELETE CASCADE,
   insight_id INT NOT NULL REFERENCES insights(id) ON DELETE CASCADE,
   PRIMARY KEY(id))
Go

This results in the warning that the cascade "may cause cycles or multiple cascade path"

So ive tried adding a cascade to just the insight_id and this results in:

The DELETE statement conflicted with the REFERENCE constraint

Any ideas?

Thanks

Daniel

解决方案

You'll have to implement this as an INSTEAD OF delete trigger on insights, to get it to work. Something like:

create trigger T_Insights_D
on Insights
instead of delete
as
    set nocount on
    delete from broader_insights_insights
    where insight_id in (select ID from deleted) or
    broader_insight_id in (select ID from deleted)

    delete from Insights where ID in (select ID from deleted)

Frequently with cascading deletes and lots of foreign keys, you need to spend time to work out a "cascade" order so that the delete that occurs at the top of a "tree" is successfully cascaded to referencing tables. But that isn't possible in this case.

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