Define candidate key, alternate key, composite key.
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Answer Posted / shruti singh
Any attribute that is uniquely identify a row in a table is
candidate key for the table. We select one of the candidate
key as Primary key. All candidate keys which are not chosen
as "primary key" are Alternate keys. The key which uniquely
identify the rows of the table and which is made up of
more than one attribute is called Composite key.
As for Example:In a class we have to select Class Monitor.
So A, B,C and D stand for that post. So A,B,C and D are
candidate for monitor so these are candidate key. We select
B as monitor so B is primary key and A,C and D can be
monitor but not selected as a monitor so they are
alternative choise. So A,C and D are alternate key.
When two students of class work together in a project than
they are composite key for the class.
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