MySQL:唯一字段需要是索引吗?

MySQL: unique field needs to be an index?(MySQL:唯一字段需要是索引吗?)

问题描述

我的表中有一个 UNIQUE 字段，我需要快速搜索它.我需要索引它吗?

I have one UNIQUE field in my table, and I need to search over it quickly. Do I need to index it?

对唯一字段和索引字段的搜索速度或资源使用情况是否有所不同?

Do searches over unique fields and indexed fields vary in speed or resource usage?

推荐答案

不需要，您不必再次索引它.当您指定 UNIQUE KEY 时，该列将被编入索引.因此它与相同类型的其他索引列(例如PRIMARY KEY)在性能上没有区别.

No, you dont have to index it again. When you specify UNIQUE KEY, the column is indexed. So it has no difference in performance with other indexed column (e.g. PRIMARY KEY) of same type.

但是如果类型不同，性能差异很小.

However if the type is different, there will be little performance difference.

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