Answers for "How to find candidate keys from a set of super keys?"
https://ask.sqlservercentral.com/questions/163893/how-to-find-candidate-keys-from-a-set-of-super-key.html
The latest answers for the question "How to find candidate keys from a set of super keys?"Answer by Pranjali13
https://ask.sqlservercentral.com/answers/163902/view.html
<div class="fr-view clearfix"><p>From all the super keys available, the candidate key is the one whose proper subset is not a super key. Let’s see it with an example.</p><p> given set of super key is:</p><p>ABC-> ABC<br />AB -> C<br />BC -> A<br />A -> BC</p><p>Given ABC key, we’re saying if we find its proper subset i.e. {A, B, C, AB, AC, BC} and any of them can be a key then ABC can’t become a candidate key.</p><p>Given ABC key, we’re saying if we find its proper subset i.e. {A, B, C, AB, AC, BC} and any of them can be a key then ABC can’t become a candidate key.</p><p>AB, which comes from the proper subset of ABC, is also a key. Therefore, ABC is not a candidate key.</p><p>Note: If x is a proper subset of y then x must NOT have one element that is included in y. Example,</p><p>X = {1,2,3} Y = {1,2,3,4}</p><p>Here, we can say X is a proper subset of Y since X doesn’t have 4 in it.</p><p>Similarly, AB is also not a candidate key because we have got A in its proper subset which can be used as a key. Therefore, at last, we found that A is the ONLY candidate key available for the above schema.</p><p>To get a detail information regarding different types of keys in dbms check out: <a href="https://www.scaler.com/topics/keys-in-dbms/">https://www.scaler.com/topics/keys-in-dbms/</a></p></div>Fri, 28 Jan 2022 10:13:44 GMTPranjali13