Attribute - It can be defined as set of all properties possessed by an entity or entity set.
Types of attributes are:
1] Simple Attributes - It is composed of single component with individual existence. simple attribute can not be further sub divided.
example, for entity employee age, salary can be simple attribute.
2] Composite attribute - An attribute composed of multiples components with independent existence is called as composite attribute.
3] Single value and multi-valued - An attribute having atomic value for a entity is called as single valued attribute.
every student have one id only. An attribute having many value, for an entity is called multi-valued attribute.
An employee may have multiple mobile numbers.
4] Stored and derived attribute -
sorted attribute - A simple attribute stored in database is called as stored attribute.
Derived attribute - A value of attribute which can be derived from related stored attribute is called derived attribute.
Null attribute - It takes null values for entities that does not have value for it.