About
A key refers to a attribute, or a group of attributes, which assumes a unique value for:
- each entity in a entity set.
- or relationship in a relationship set.
A key is an identifier only for its local scope (ie inside a entity or relationship set). More … see Identifier
Example
Management
List
- Logical Data Modeling - Primary Key (Id, Name) - A primary key is that candidate key which will most commonly be used to uniquely identify a single entity instance.
- alternate key - Any candidate key that is not selected to become the primary key is called an alternate key.
- concatenated key - A group of attributes that uniquely identifies an entity is called a concatenated key.
Data Type
An identifier data type must be able to hold any key value.
A common implementation of this data type is an integer (64 bit :))