Classification of Attributes in DBMS

1.???? Simple Attribute:

• A simple attribute is an attribute that cannot be divided further.
• Example: Age attribute in an employee table. Each employee can have only one age.

2.???? Composite Attribute:

• A composite attribute is an attribute that can be further divided into sub-parts.
• Example: Name attribute in an employee table divided into first name, middle name, and last name.

3.???? Single-Valued Attribute:

• A single-valued attribute is an attribute that can have only one value for a particular entity.
• Example: Age attribute is usually a single-valued attribute as a person typically has only one age.

4.???? Multi-Valued Attribute:

• A multi-valued attribute is an attribute that can have more than one value for a particular entity.
• Example: Phone number attribute in an employee table, where an employee can have multiple phone numbers.

5.???? Stored Attribute:

• A stored attribute is one where the value is explicitly stored in the database.
• Example: Name attribute in an employee table where names like Bob, Alice, and Sam are directly stored in the database.

6.???? Derived Attribute:

• A derived attribute is one whose value is calculated or derived from other stored attributes.
• Example: Age attribute in an employee table, calculated from the Year of Birth (YOB) attribute using a formula like current year minus YOB.

7.???? Complex Attribute:

• A complex attribute is an attribute that is both composite and multi-valued in a database design. A composite attribute is one that can be divided into sub-parts, while a multi-valued attribute can have multiple values for a single entity. When an attribute exhibits both characteristics - being composite and multi-valued - it is classified as a complex attribute.
• Example:

In the employee entity, the Address attribute can be a complex attribute. This is because the Address attribute can have multiple values for an employee (multi-valued) if an employee has more than one residence. Additionally, the Address attribute can be further divided into sub-parts like door number, street number, and pin code (composite), making it a complex attribute due to its composite and multi-valued nature.

Examples of combinations of attribute classifications:

1. ???Simple and Single-Valued Attribute: Age attribute can be both a simple attribute (cannot be divided further) and a single-valued attribute (only one value per entity).
2. Simple and Multi-Valued Attribute: Phone number attribute can be both a simple attribute (indivisible) and a multi-valued attribute (multiple values per entity).
3. Composite and Single-Valued Attribute: Name attribute can be both a composite attribute (divided into sub-parts like first name, middle name, last name) and a single-valued attribute (one name per entity).
4. Composite and Multi-Valued Attribute: An attribute that is composite and multi-valued means that it can be divided into sub-parts and also have multiple values for a particular entity. Example: Address attribute in a customer table, where the address can be divided into street, city, state, and zip code, and a customer may have multiple addresses.
5. Stored Simple Single-Valued Attribute: Employee ID attribute is a simple, single-valued attribute stored directly in the database.
6. Stored Simple Multi-Valued Attribute: Skills attribute for an employee can be a simple attribute stored directly but with multiple skill values.
7. Stored Composite Single-Valued Attribute: Birthplace attribute can be composite with sub-parts like city and country, but only one birthplace per entity.
8. Stored Composite Multi-Valued Attribute: Education Details attribute can be composite with sub-parts like degree, institute, year, but with multiple values for different degrees.
9. Derived Simple Single-Valued Attribute: Tenure attribute can be derived from the start date and current date for an employee.
10. Derived Simple Multi-Valued Attribute: Performance Ratings attribute can be derived based on evaluation scores over different periods.
11. Derived Composite Single-Valued Attribute: Full Address attribute can be derived from the sub-parts like street, city, state, zip code.
12. Derived Composite Multi-Valued Attribute: Project Contributions attribute can be derived from contributions on multiple projects over time, with each project having its own set of details.

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