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What are partial, alternate,, artificial, compound and natural key?
Partial Key: It is a set of attributes that can uniquely recognize weak entities and that are related to same owner entity. It is sometime known as Discriminator.
Alternate Key: All Candidate Keys excluding the Primary Key are called as Alternate Keys.
Artificial Key: If no obvious key either stands alone or compound is available, then the last resort is to simply make a key, by assigning a unique number to every record or occurrence. Then this is known as developing an artificial key.
Compound Key: If no single data element uniquely identifies occurrences within a construct, then combining multiple elements to make a unique identifier for the construct is known as creating a compound key.
Natural Key: When one of the data elements stored within a construct is utilized as the primary key, then it is known as the natural key.
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Can a filed occur in several field groups. Yes. But it leads to redundant data redundancy.
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