Used in ER diagrams; if you think of the contents of an entity as a series of rows in a table, the primary key is the field containing the unique identifier for each row For example, in the entity Invoice there is a row of data for each invoice, and the field Invoice Number could serve as the primary key, which uniquely identifies a given invoice
The Key chosen by the database designer to be VA FileMan's principal means of identifying records in the file VA FileMan automatically displays the Primary Key during classic interactive lookup (^DIC) and uses the Primary Key to identify records brought in during a KIDS installation Exactly one Key in a file or subfile must be designated the Primary Key See Key
A column, or combination of columns, within a table whose values together form the "principal unique identifier" of rows in that table In other words, a table's primary key serves to uniquely identify row in that table
An attribute in an entity that uniquely identifies rows of that entity For example, the Employee entity can contain an empID attribute that uniquely identifies each employee
An attribute selected to act as the unique identifier for each occurrence of an entity or relationship A primary key must be unique, stable, minimal and non-null under all conditions
An attribute or group of attributes that uniquely identifies a tuple within a table Example: A customer table might have as its primary key the customer number
Every table should have one field (attribute) which is unique to each record, or at least some combination of fields which taken together are unique to each record There is no other way to distinguish a single record reliably This field or combination is called the primary key
A column or number of columns that uniquely identifies a row in a table; i e a primary key value cannot occur more than once in a table Therefore a primary key must be unique and not contain null values A Cadidate Key is a good choice for the primary key of a table
An attribute (or combination of attributes) that uniquely identifies each row in a relation (6) See also Composite key, Foreign key, Identifier, Index, Secondary key