避免循环依赖：MySQL/实体框架
我们在处理循环依赖时遇到了麻烦，想知道是否有人可以提出解决方案。如果我们想删除一个客户端，实体框架会拒绝这样做，因为它告诉我们外键约束失败。我们的表格设置如下：
ClientAccounts
Id [PK]
Forenames
Surname
DefaultEmailId [FK, NULLABLE]
ClientEmailAddresses
Id [PK]
Description
EmailAddress
ClientId [FK, NON-NULLABLE]
因此，客户可以拥有与其关联的零个或多个电子邮件地址帐户。其中之一将是他们的默认联系电子邮件地址。
我认识到，如果我们允许 ClientEmailAddresses 表有一个空的 ClientId，它就可以正常工作；但我们不希望出现孤立电子邮件记录的情况。
We're having trouble dealing with a circular dependancy and wondered if anyone could suggest a solution. If we want to delete a client, entity framework refuses to do this because it tells us a foreign key constraint fails. Our tables are setup like this:
ClientAccounts
Id [PK]
Forenames
Surname
DefaultEmailId [FK, NULLABLE]
ClientEmailAddresses
Id [PK]
Description
EmailAddress
ClientId [FK, NON-NULLABLE]
So a Client can have zero or many email addresses associated with their account. One of which will be their default contact email address.
I recognise that if we allowed the ClientEmailAddresses table to have a null ClientId, it would work ok; but we don't want a situation where we could have orphan email records.
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也许最好将“default”字段存储在表 ClientEmailAddresses 中，并从表 ClientAccounts 中删除 DefaultEmailId。我不知道你的代码结构，但有时像你这样的结构是多余的。
Maybe it's better to store field 'default' in table ClientEmailAddresses and remove DefaultEmailId from table ClientAccounts. I don't know your code structure but sometimes structure like yours is redundant.
您是否应该首先删除 ClientEmailAddresses 中的条目？
想象一下这样的存储过程：
其中 Id2delete 是要删除的客户端 ID。
我没有尝试过，但应该可以！
Shouldn't you first delete the entries in ClientEmailAddresses ?
Imagine a stored procedure like this :
where Id2delete is the client ID to delete.
I haven't try, but should work !