Evaluation to candidate keys by functional dependencies in the database 数据库中利用函数依赖求解候选码的方法
2.
The tool makes creating these keys easy by automatically providing a lookup on the valid candidate keys defined in the columns view 该工具通过自动提供查找columns视图中定义的有效备选键，从而很容易地创建这些键。
3.
The reason is that the results are unpredictable unless you always group by a primary or candidate key value because you cannot know which value from the non - grouped data will be selected 这个原因是因为结果是不可预知的，除非你允许以主关键字或是候选关键字来作为分组，因为你无法知道which将从哪能一个非分组的数据作选取。
