Which three pieces of information did E.F. Codd describe as necessary to retrieve a data value from a relational database?
Attribute, domain, and tuple
Entity, relation name, and domain
Table name, primary key, and entity
Attribute, relation name, and primary key
Which statement best describes a candidate key?
It is the primary key for an entity.
It uniquely identifies every instance of an entity.
One or more keys are joined together to form a composite key.
One or more keys may be used to form a primary key.
