updated: 2022-01-23_12:32:31-05:00

Primary Key

Individual entities are distinct
Type of Key

It's the chosen Candidate Key, taken from Superkey, the set of key groups able to identify unique rows

For a relationship, usually it's the union of two primary keys

Binary Relationships & PK

• many to many
  • union of primary keys is a minimal super key is chosen as the primary key
• one to many
  • primary key of the many side is a minimal superkey
• one to one
  • primary key can be either one of the participating entity sets
  • either one can be chosen as the primary key