Logical Data Modeling - Key

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.

• database primary key,
• database unique key,

• 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.
• Logical Data Modeling - Unique Key
• Logical Data Modeling - (Surrogate | Substitute | Synthetic) Primary key
• Logical Data Modeling - Natural Key
• Logical Data Modeling - Business Key
• 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.

An identifier data type must be able to hold any key value.

A common implementation of this data type is an integer (64 bit :))

• Asktom
• Object_identifier