存在无法在具有自引用约束的表上设置 ON DELETE CASCADE 的情况.存在循环逻辑问题的可能性，因此不允许.

It is the case that you cannot set up ON DELETE CASCADE on a table with self-referencing constraints. There is a potential of cyclical logic problems, hence it won't allow it.

有一篇很好的文章这里 - 不过它适用于 SQL 的第 8 版而不是第 9 版 - 尽管适用相同的规则.

There's a good article here - though it's for version 8 rather than 9 of SQL - though the same rules apply.