what is the difference between primary key & foreign key?
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Answer Posted / pravin
The primary key of a relational table uniquely identifies
each record in the table. It can either be a normal
attribute that is guaranteed to be unique (such as Social
Security Number in a table with no more than one record per
person) or it can be generated by the DBMS (such as a
globally unique identifier, or GUID, in Microsoft SQL
Server). Primary keys may consist of a single attribute or
multiple attributes in combination.
Examples:
Imagine we have a STUDENTS table that contains a record for
each student at a university. The student's unique student
ID number would be a good choice for a primary key in the
STUDENTS table. The student's first and last name would not
be a good choice, as there is always the chance that more
than one student might have the same name.
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