问题描述
可能重复:
外键有什么问题?
我使用带有大约 4 GB 数据的大型数据库的 MS Sql Server.
I use MS Sql Server with a large database about 4 GB data.
我在网上搜索为什么我应该使用外键.到目前为止，我只索引了用于连接表的键.性能很好，数据完整性没问题.
I search around the web why I should use foreign keys. by now I only indexed the keys used to join tables. Performance is all fine, dataintegrety is no problem.
我应该使用外键吗?使用外键会获得更高的性能吗?
Should I use foreign keys? Will I get even more performance with foreign keys?
推荐答案
外键实际上并没有提高性能，实际上它们会在所有写入操作上产生很小的性能损失，以确保遵循约束.
Foreign key's don't actually improve performance, in fact they incur a small performance penalty on all write operations, to ensure that the constraint is followed.
您要使用这些的原因是为了防止破坏性的写入操作.如果您没有它们，错误代码或错误的 sql 语句可能会删除预期存在的行.
The reason why you want to use these is to prevent destructive write operations. If you don't have them, buggy code, or a bad sql statement can remove rows that are expected to be there.
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