In database design, finding the candidate key is an essential part of creating a well-structured database. The candidate key is the attribute or combination of attributes that uniquely identify each row in a table. The rest of the design of a database, including normalization, depends on the candidate key. Therefore, it is crucial to find the candidate key correctly.
To find the candidate key from a given set of functional dependencies, we first need to understand the set. The set of functional dependencies consists of a set of attributes and their dependencies. For example, if A determines C, then whenever we have A, we also have C.
To find the candidate key, we need to identify the attributes that cannot be determined from the set of functional dependencies. In other words, if an attribute is not present on the right-hand side of any dependency, it must be present in the candidate key. For example, if we have A determines C, C determines D, and B determines E, we cannot determine A, B, and E from the set. Therefore, they must be present in the candidate key.
Once we have identified the attributes that must be present in the candidate key, we need to check if any other attributes are also required to form the set of candidate key. To do this, we need to find the closure of the attributes. The closure is the set of attributes that can be determined from a given set of attributes. For example, if we have A determines B and B determines C, the closure of A is ABC.
In the example mentioned above, we can determine all the attributes with the help of A. Therefore, the candidate key is AEACBDF. However, in some cases, we may need to check all possible combinations to find the candidate key.
In conclusion, finding the candidate key from functional dependencies is an essential step in database design. It is crucial to identify the attributes that must be present in the candidate key and check for any other required attributes. By following these steps, we can create a well-structured and normalized database.