Entities are represented by means of their properties called attributes. All attributes have values. For example, a student entity may have name, class, and age as attributes.
There exists a domain or range of values that can be assigned to attributes. For instance, a student's name cannot be a numeric value. It has to be alphabetic. A student's age cannot be negative, etc.
Types of Attributes in DBMS
1. Simple attribute: Simple attributes are atomic values, which cannot be divided further. For instance, a student's phone number is an atomic value of 10 digits.
2. Composite attribute: Composite attributes are made of more than one simple attribute. For instance, a student's complete name may have first_name and last_name.
3. Derived attribute: Derived attributes are the attributes that do not exist in the physical database, but their values are derived from other attributes present in the database. For instance, average_salary in a department should not be saved directly in the database, instead it can be derived. For a further example, age can be derived from data_of_birth.
4. Single-value attribute: Single-value attributes contain single value. Example: Social_Security_Number.
5. Multi-value attribute: Multi-value attributes may include more than one values. For instance, a person can have more than one phone number, email_address, etc.
Attribues can be in form of:
1. Simple single-valued
2. Simple multi-valued
3. Composite single-valued
4. Composite multi-valued
2. Composite attribute: Composite attributes are made of more than one simple attribute. For instance, a student's complete name may have first_name and last_name.
3. Derived attribute: Derived attributes are the attributes that do not exist in the physical database, but their values are derived from other attributes present in the database. For instance, average_salary in a department should not be saved directly in the database, instead it can be derived. For a further example, age can be derived from data_of_birth.
4. Single-value attribute: Single-value attributes contain single value. Example: Social_Security_Number.
5. Multi-value attribute: Multi-value attributes may include more than one values. For instance, a person can have more than one phone number, email_address, etc.
Attribues can be in form of:
1. Simple single-valued
2. Simple multi-valued
3. Composite single-valued
4. Composite multi-valued
No comments:
Post a Comment