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MariaDB 在没有外键关系的行上删除 CASCADE

[英]MariaDB On delete CASCADE on rows without foreign key relationship

原文 2020-08-06 09:38:29 6 1 mysql/ triggers/ mariadb/ cascade

I have a problem I've been cracking my head over the last few days.我有一个问题，在过去的几天里我一直在头疼。 I have a relational DB (mariaDB), which has two tables.我有一个关系数据库（mariaDB），它有两个表。 Table A and table B. Table A has a relation with itself, and when one row is deleted, multiple MAY be deleted (via on delete CASCADE).表A和表B。表A和自己有关系，当删除一行时，可能会删除多个（通过on delete CASCADE）。 Table B has no relation with table A. I cannot create a relation, as the rows currently present in the tables may or may not have the correct (to enforce this relation) data in it (I have no influence over this).表 B 与表 A 没有关系。我无法创建关系，因为表中当前存在的行可能有也可能没有正确的（强制这种关系）数据（我对此没有影响）。

When I delete a record from table A, I would like the implicitly related data from table B to also be deleted.当我从表 A 中删除一条记录时，我希望表 B 中的隐式相关数据也被删除。 As a foreign key cannot be created, a on delete CASCADE seems impossible.由于无法创建外键，因此删除 CASCADE 似乎是不可能的。 I thought of a trigger, which would find relevant rows on every delete from table A, however, triggers will not fire on rows deleted by a on delete CASCADE.我想到了一个触发器，它会在表 A 中的每次删除时找到相关行，但是，触发器不会在由 on delete CASCADE 删除的行上触发。 Meaning that when row X (from table A) gets deleted as a result of a CASCADE, the relevant data from table B will not be deleted.这意味着当 X 行（来自表 A）由于 CASCADE 被删除时，表 B 中的相关数据将不会被删除。

If I had to summarize this to a question: Is it possible to delete a row, like on delete CASCADE, without the use of foreign keys or triggers?如果我不得不将其总结为一个问题：是否可以在不使用外键或触发器的情况下删除一行，例如在删除 CASCADE 时？

Thanks for reading, appreciate it!感谢阅读，不胜感激！

1 个解决方案

Thanks to @Akina.感谢@Akina。

Iterate over rows relevant to the one deleted in the trigger, and then delete all rows relevant to those rows in table B. This works, but I cannot accept my own answer as of yet.迭代与触发器中删除的行相关的行，然后删除与表 B 中这些行相关的所有行。这可行，但我目前还不能接受我自己的答案。