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Is there any difference between primary key (which is a composite key) and a prime attribute?
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An attribute that is a part of one of the candidate keys is known as prime attribute. Example: Suppose a company wants to store the complete address of each employee, they.
Attributes are basically used to differentiate one entity from another. When we chose an attribute or set of attributes to distinctly identify entities in entity sets, they are called keys.
This unique standard attribute is called a primary-key attribute. The primary-key attribute and a value assigned to a record becomes the primary key of the record. Every record added to the data store must have a primary key.
Please note: prime attribute is an attribute that is part of any candidate key. Non prime attribute is an attribute that is not part of any candidate key. So, its advisable that you find out all possible candidate keys from the given functional dependencies and mark the prime and non prime attributes.
A candidate key is a key that uniquely identifies rows in a table. Any of the identified candidate keys can be used as the table's primary key. Candidate keys that are not part of the primary key are called alternate keys. One can describe a candidate key as a super key that contains only the minimum number of columns necessary to determine uniqueness.
Prime attributes are the attributes of the candidate key which defines the uniqueness (Eg: SSN number in an employee database)
A primary key is a column in a table whose values uniquely identify the rows in the table. The primary key is chosen from this list of candidates based on its perceived value to the business as an identifier.
A primary key value:
If the primary key is a combination of more than one column then it is called as composite key.
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