What are partial, alternate,, artificial, compound and natural key?

Partial Key:

It is a set of attributes that can uniquely identify weak entities and that are related to same owner entity. It is sometime called as Discriminator.

Alternate Key:

            All Candidate Keys excluding the Primary Key are known as Alternate Keys.

Artificial Key:

 If no obvious key, either stand alone or compound is available, then the last resort is to simply create a key, by assigning a unique number to each 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 create 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 called the natural key.