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Derived attribute in DBMS
Derived Attribute in DBMS
On this page, we will learn about Derived Attribute in DBMS.
A derived attribute as the name suggests is the one that can be
derived or calculated with the help of other attributes present themselves.
For example – The age of the student can be calculated from
‘date of the birth present as an attribute.
Representation: Horizontal Dashed Oval
Definition of a derived attribute
- A derived attribute data is derived (copied) from the attribute of another table
- The derived attribute value is always dynamic.
Example of a derived attribute
If you need to copy the age data from another table to the student table then and age attribute will become derived attribute in the student table
Representation of derived attribute
In the ER diagram, the derived attribute is represented by a dashed oval with a name inside the dashed oval
Derived vs Stored Attribute
| Stored Attribute | Derived Attribute |
|---|---|
| It must be explicitly stored in database | It may not be explicitly stored as it can be derived from another attribute |
| It is not possible to determine stored attribute value from another attribute | It is possible to determine derived attribute value from another attribute |
| Stored attribute will be fixed. | Derived attribute will be variable in nature |
| Represented by an oval | Represented by a dotted oval |
| Since, value is direct it saves CPU time | CPU time is consumed in derivation from another attribute |
| It saves data access time | if it is not stored in the Relational table, then the data access time is longer |
| Requires constant maintenance. To keep the most updated value. Also in order to make sure that its parallel derived attribute has latest value | Derived attribute may not need maintenance. However, its parallel stored attribute may need it. |
| Does not add coding complexity to queries | Adds coding complexity to queries, if not stored in the Relational table |
| Readily available value | data value is not readily available, if not stored in the Relational table |
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