下面设想的一般准则是什么:
你们需要建立一个表格,说明PK是外部系统产生的价值。 它是独特的,类似于使用SSN。
这是主要的关键吗? 尤其考虑到这一信息将被用于与另外两个表格的外国关键关系。 或者,除了独特的钥匙外,还要建立一个自动加固的身份证场,并在表格关系中使用自动加固的身份证,是否更好?
从个人角度来说,我不相信外部系统提供的身份证。 他们今天向你们保证,这将是独一无二的,永远不会改变,永远不会再重复。 但是,今后有一天......
创建自己的自动加固身份,并用于PK和FK关系。 仅供参考。
我将永远建立自己对主要钥匙的代议制,并将自然识别作为次要的独特关键。
Scott W Ambler对以下两项战略进行了很好的比较:here。
利用自己的汽车 我将在一份表格中向你们提供另一个领域,提供过多的信息。 如果外部身份证与SSN一样,我认为你不会收到重复。 我选择将外部身份证作为PK。
$db_user="root"; $db_host="localhost"; $db_password="root"; $db_name = "fayer"; $conn = mysqli_connect($db_host,$db_user,$db_password,$db_name) or die ("couldn t connect to server"); // perform query ...
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Is it because of size? By the way, what is the limit of the size?
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