An attribute is used to represent special characteristics of an entity. On the basis of attributes one entity is differ from another entity.In other words, we can say that an attribute is column/field/property of any entity set/table and obey applied rules and conditions of company or organization.attributes are represented by ellipse/oval symbol.
Example:- aadhar no., name, dob, address, photo, QR code, email id, mob_no. Etc. Are the attributes of any person (Indian).
Attributes are of following types -
1. Simple attribute
2. Composite attribute
3. Single value attribute
4. Multi value attribute
5. Null attribute
6. Derived attribute
1. Simple attribute :- simple attribute is that attribute of any entity, which can not be divided into sub-parts. It means simple attribute always stores atomic value.
Example :-
A. Roll no. , blood group, marks, mob_no., gender, marks etc of a student.
B. EmployeeID, designation, salary etc. of an employee.
2. Composite attribute :- composite attribute is that attribute of any entity which can be divided into sub parts. It means a composite attribute is collection of more than one simple attribute.
Example :- full name attribute of student can be divided into three parts, first name, middle name & last name. similarly, attribute of employee's address can be divided into house no., lane no., street, city, country and pin code.
3. Single value attribute :- an attribute which stores only one value for every entity/record/touple/row is called single value.
Example:- roll no., enrollment no., gender, dob, transaction id, blood group etc. Of student.
4. Multi value attribute :- an attribute which more than one value for every entity/record/row/touple is called multi value attribute.
Example :- mob_no., email id, experience, hobbies, interest, address etc.
5. Null attribute :- null attribute is an attribute in which value of attribute doesn't receive then stores null value. This work is done in an special state. Null value is different from zero and blank space.
6. Derived attribute :- an attribute whose value doesn't depend on value of any attribute is called derived attribute. Derived attribute is represented by dashed oval.
Example:- for age attribute of any person it depends on dob attribute of that person and present_date.
Profit/loss attribute of any product depends on cost price and sell price attribute of that product.
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