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hi,i want t0 knom d syntax for a super key with an example
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Answer Posted / shikha
PersonID
PersonID + LastName
PersonID + FirstName
PersonID + DOB
PersonID + LastName + FirstName
PersonID + LastName + DOB
PersonID + FirstName + DOB
PersonID + LastName + FirstName + DOB
LastName + FirstName + DOB
All of these will uniquely identify each record, so each
one is a superkey. Of those keys, a key which is comprised
of more than one column is a composite key; a key of only
one column is a simple key.
A candidate key is a superkey that has no unique subset; it
contains no columns that are not necessary to make it
unique. This table has 2 candidate keys:
PersonID
LastName + FirstName + DOB
Not all candidate keys make good primary keys: Note that
these may work for our current data set, but would likely
be
.
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