Set of solved exercises in Normalization / Normalization Solved Examples / How to find candidate keys, and primary keys in database? / Sets of examples to find the keys of a tables / Process of Key finding in a database - Examples
- From D → B, D cannot uniquely determine the values of all the other attributes. Hence, D alone cannot be a candidate key.
- From BC → ADE, it is very clear that if you know values of B and C, you can determine the values of attributes A, D, and E. Hence, BC → ABCDE is holding. So, BC is one candidate key.
- From D → B, if you know D then you know B. If you know C also, then you can determine all the other attributes. Hence, CD is another candidate key.
- Let us try this example with the algorithm that is used for finding Attribute Closure. Click in the above link to visit the page.
- Let us start with AB. Assume that the result is AB.
- Let us try with the other combination ABD.
- Let us try with the other combination BCD.