Can a key be the set of all attributes if there is at least one nontrivial FD in a schema?
What will be an ideal response?
```
No. Suppose a key k contained all attributes and there is a non-trivial FD X ? Y . k contains X and Y . But the FD implies that X determines Y . Hence we can delete Y ? (X ? Y )fromk and the remaining attributes still form a key. This means that k was not minimal, a contradiction.
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Computer Science & Information Technology
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