我正在创建一个数据库表,我没有给它分配一个逻辑主键。每个表都应该有一个主键吗?
当前回答
Will you ever need to join this table to other tables? Do you need a way to uniquely identify a record? If the answer is yes, you need a primary key. Assume your data is something like a customer table that has the names of the people who are customers. There may be no natural key because you need the addresses, emails, phone numbers, etc. to determine if this Sally Smith is different from that Sally Smith and you will be storing that information in related tables as the person can have mulitple phones, addesses, emails, etc. Suppose Sally Smith marries John Jones and becomes Sally Jones. If you don't have an artifical key onthe table, when you update the name, you just changed 7 Sally Smiths to Sally Jones even though only one of them got married and changed her name. And of course in this case withouth an artificial key how do you know which Sally Smith lives in Chicago and which one lives in LA?
你说你没有自然的密钥,因此你也没有任何字段的组合来使其唯一,这使得人工密钥至关重要。
我发现,在没有天然密钥的情况下,人工密钥对于维护数据完整性是绝对必要的。如果您确实有一个自然键,您可以使用它作为键字段。但就我个人而言,除非自然键是一个字段,否则我仍然喜欢人工键和自然键上的唯一索引。如果你不放进去,你以后会后悔的。
其他回答
为了证明未来,你真的应该这么做。如果你想复制它,你需要一个。如果你想把它加入到另一张桌子上,你的生活(以及那些明年不得不维持它的可怜的傻瓜们的生活)将会轻松得多。
只要添加就可以了,以后你会后悔没有(选择,删除)。连接等)
我知道为了在。net中使用gridview的某些特性,你需要一个主键,以便gridview知道哪一行需要更新/删除。一般的做法应该是有一个主键或主键集群。我个人更倾向于前者。
我总是有一个主键,即使一开始我还没有想到它的目的。有几次,当我最终需要在一个没有PK的表中输入PK时,总是会遇到更多的麻烦。我认为总是有一个人会有更多的好处。
Will you ever need to join this table to other tables? Do you need a way to uniquely identify a record? If the answer is yes, you need a primary key. Assume your data is something like a customer table that has the names of the people who are customers. There may be no natural key because you need the addresses, emails, phone numbers, etc. to determine if this Sally Smith is different from that Sally Smith and you will be storing that information in related tables as the person can have mulitple phones, addesses, emails, etc. Suppose Sally Smith marries John Jones and becomes Sally Jones. If you don't have an artifical key onthe table, when you update the name, you just changed 7 Sally Smiths to Sally Jones even though only one of them got married and changed her name. And of course in this case withouth an artificial key how do you know which Sally Smith lives in Chicago and which one lives in LA?
你说你没有自然的密钥,因此你也没有任何字段的组合来使其唯一,这使得人工密钥至关重要。
我发现,在没有天然密钥的情况下,人工密钥对于维护数据完整性是绝对必要的。如果您确实有一个自然键,您可以使用它作为键字段。但就我个人而言,除非自然键是一个字段,否则我仍然喜欢人工键和自然键上的唯一索引。如果你不放进去,你以后会后悔的。
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