Set of attributes (columns) that uniquely specify a tuple (row) in a relation
Also known as primary key constraint
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4 identifiers linking primary key across the web's reference databases
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In the relational model of databases, a primary key is a designated set of attributes that can reliably identify and distinguish between each individual record in a table. The database creator can choose an existing unique attribute or combination of attributes from the table to act as its primary key, or create a new attribute containing a unique ID that exists solely for this purpose.