Attribute must have atomic data that helps to simplifies SQL Query Operation and avoid Database Anomalies. In the Entity Relationship Model, a Multivalued Attribute is defines a group of data. We need to analyze and eliminate repeating group of data from one entity that decompose into two different entities to produce atomic data.
An instance, an I.T. Company Technical Department is formed with many Employees and each Employee has many Technical Skills that maintain in the Employee Entity. Technical Skills is a repeating group of data in the Employee entity that need to isolate from Employee entity into Employee Skill entity to produce atomic data.
Derived attribute data is generates from dependent attribute's data through Calculation or Algorithm or Procedure. Derived attribute is an option attribute in the Relational Database that helps to optimize database operation. An instance, Age attribute data can generates through Calculation with dependent attribute's Date of Birth and Today Date.
Decoded attribute is used to maintain unique redundant data, instead to maintain actual data in the attribute. Decode data is formed with single or collection of alphanumeric data that helps to reduce database memory and optimize database operation.
An instance, Activate_Status attribute is used to maintain "Activated" or "Deactivated" data, instead to maintain actual data in the attribute, we can maintain "A" mean Activated and "D" mean Deactivated data. Database Management System is provides DECODE Function that helps to produces actual data.
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