What is the Difference Between Stored and Derived Attribute in DBMS

The main difference between stored and derived attribute in DBMS is that it is not possible to find the value of a stored attribute using other attributes while it is possible to find the value of a derived attribute using other attributes.  

Database Management System (DBMS) is a software that allows storing and managing data efficiently. It stores data in tables; these tables are also called entities. Each table has attributes. The attributes define the characteristics or properties of an entity. For example, a student table can have attributes such as id, name, age, location, etc. There is various type of attributes. Two of them are stored and derived attribute.

Key Areas Covered

1. What is a Stored Attribute in DBMS
     – Definition, Functionality
2. What is a Derived Attribute in DBMS
     – Definition, Functionality
3. What is the Relationship Between Stored and Derived Attribute in DBMS
     – Outline of the Association
4. What is the Difference Between Stored and Derived Attribute in DBMS
     – Comparison of Key Differences

Key Terms

Attributes, DBMS, Derived Attribute, Stored Attribute

What is a Stored Attribute in DBMS

When it is not possible to determine the value of an attribute using another attribute, then that attribute is called a stored attribute. For example, assume a table called Employee. There are attributes such as emp_id, name, department, location, etc. We cannot identify the values of these attributes using other attributes. Therefore, we call these stored attributes. In an ER diagram, we can represent a stored attribute using an oval with a solid line.

What is a Derived Attribute in DBMS

When it is possible to determine the value of an attribute using another attribute, then it is called a derived attribute. We can remove a derived attribute from the table, but we can also keep that attribute to improve understandability. For example, the Employee entity can also have attributes such as date_of_birth and age. We can drive age using the attribute data_of_birth. Therefore, age is a derived attribute.  If required, it is also possible to eliminate the age attribute from the table. In an ER diagram, we can represent a derived attribute using an oval with dotted lines.

Figure 1: ER Diagram with Stored and Derived Attributes

In the above ER diagram, Employee is the entity. Moreover, id, name, and date_of_birth are stored attributes while age is a derived attribute.

Relationship Between Stored and Derived Attribute in DBMS

• We can obtain a derived attribute using a stored attribute.

Difference Between Stored and Derived Attribute in DBMS

Definition

A stored attribute is an attribute that cannot be derived from other attributes while a derived attribute is an attribute that can be obtained using another stored attribute. Thus, this is the main difference between stored and derived attribute in DBMS.

Determining the Value

Also, an important difference between stored and derived attribute in DBMS is that we cannot determine the value of a stored attribute. However, we can determine the value of a derived attribute using another attribute.

Type

Furthermore, stored attributes are fixed, but derived attributes are variable in nature. Hence, this is another difference between stored and derived attribute. 

Storage

Besides, it is compulsory to store the stored attributes on the database, but it is not compulsory to store a derived attribute on the database.

Example

For example, date_of_birth is a stored attribute while age is a derived attribute. 

Conclusion

DBMS stores data in tables or entities. Each entity has attributes that describe it. The two types of attributes are stored and derived attributes. The main difference between stored and derived attribute in DBMS is that it is not possible to find the value of a stored attribute using another attribute while it is possible to find the value of a derived attribute using another attribute. 

Reference:

1. McFadyen, Ron. “Stored Attributes.” Entity Relationship Modeling, University of Winnipeg, Available here.
2. McFadyen, Ron. “Derived Attributes.” Entity Relationship Modeling, University of Winnipeg,
Available here.
3. “Basic Concepts of ER Model in DBMS.” Types of Network Topology in Computer Networks | Studytonight, Available here.