Tuesday, May 3, 2011

Keys - VII


Primary Key
The primary key is a unique identifier for a record.  The primary key cannot be the same for two records.  This field can never be blank.
Primary Key
Composite Key
A composite key is a primary key that is comprised of two or more fields.  It can also be called a compound or concatenated key. 
Foreign Key
A foreign key is a field or combination of fields that are related to the primary key of another table.

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