将其理解为：“X唯一确定Y”，这也意味着Y在功能上依赖于X。
这里示例的几种检测功能依赖的方式为：
- Functional Dependencies Derived from Keys
- Functional Dependencies Derived from Multiple-Column Keys and from Equalities
- Functional Dependency Special Cases
- Functional Dependencies and Views
- Combinations of Functional Dependencies
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