L＆H_Reader新闻阅读器？(L&H_Reader news reader? What's this?)

 你正在使用什么样的数据库模式？ 通常，这是关系应该存储的地方，我认为这应该在数据处理级而不是代码上。 
 
 这是一个非常简单的建议 
 
 保险（<insurance_id>，名称，说明） 
 
 insurance_item（<item_id>，<insurance_id>，名称，说明） 
 
 insurance_item_details（<item_id>，<policy_id>，when_changed） 
 
 insurance_policy与insurance_item有一对多的关系。 insurance__item与insurance_item_details有一对多的关系。 insurance__item__details中的每一行代表政策的变化。 
 
 这样，SQL可以快速检索最新的两个项目 
 
SELECT FROM insurance_item_details, insurance_item, insurance where
             insurance_item_details.item_id = insurance_item.item_id
             AND insurance_item.insurance_id = insurance.insurance_id
             ORDER BY when_changed
             LIMIT 1
 
 或者你甚至可以检索历史。 
 
 （该SQL尚未尝试过） 
 
 因此，您的想法是不重复insurance_item - 您有另一个表来存储将被更改的元素，并用它拍摄一个时间戳，将该更改表示为关系。 
 
 我不是SQL专家（不幸），但是你只需要插入到insurance_item_details表中，而不是复制副本。 从它看起来的方式来看，像我最初的例子那样制作副本似乎违反了2NF，我想。 

Thanks everyone who has provided answers. Unfortunately, due to conditions at work I'm unable to implement database changes and am stuck trying to make due with a coding solution.
 
After spending some time over the weekend on this problem I have come up with a solution that I believe simplifies the code a bit even though it is still nowhere near perfect.
 
I extracted the functionality out into a new method and pass in the master policy that I want the new policy linked to.
 
Policy Convert(Policy policy, Policy masterPolicy)
{
    Policy newPolicy = policyManager.Copy(policy);

    //link the policy to it's master policy
    if(masterPolicy != null)
    {
        newPolicy.MasterPolicyId = masterPolicy.Id;
    }

    SavePolicy(newPolicy);

    //inactivate the current policy
    policy.Status = Inactive;
    policyManager.UpdatePolicy(policy);

    return newPolicy;
}
 
This allows me to then loop through all the policies and pass in the policy that needs to be linked as long as the policies are sorted in the correct order...which in my case is by start date and then by master policy id.
 
Policy newPolicy = null;
foreach(Policy policy in policyList)
{
    Policy masterPolicy = policy.MasterPolicyId.HasValue ? newPolicy : null;
    newPolicy = Convert(policy, masterPolicy);   

}
 
When all is said and done, it isn't all that much less code but I believe it is much more understandable and it allows individual policies to be converted.