Types of Attributes in DBMS with Example (ER MODEL – Part-2)

Attribute : It is the name of the column. An attribute gives the characteristics of the entity. For example, A customer of bank may be described by : name, address, customer ID number. It is also called as data element, data field, a field, a data item, or an elementary item.

Type of Attributes in DBMS –

Type of Attributes in DBMS

Single valued Attributes : An attribute, that has a single value for a particular entity is known as single valued attributes. For example, age of a employee entity.

Multi valued Attributes : An attributes that may have multiple values for the same entity is known as multi valued attributes. For example colors of a car entity.

Compound Attribute/Composite Attribute : Attribute can be subdivided into two or more other Attribute. For Example, Name can be divided into First name, Middle name and Last name.

Simple Attributes/Atomic Attributes : The attributes which cannot be divided into smaller subparts are called simple or atomic attributes. For example, age of employee entity

Stored Attribute : An attribute, which cannot be derived from other attribute, is known as stored attribute. For example, BirthDate of employee.

Derived Attribute : Attributes derived from other stored attribute. For example age from Date of Birth and Today’s date.

  • An attribute can be derived from a single attribute. Example age from DOB and current date.
  • An attribute can be derived from multiple attribute.
  • An entity can be derived from a separate table. Example,
    RNO Name DeptNO
    1 A 1
    2 B 1
    3 C 2
    4 D 3
    5 E 1
    DNO Dname
    1 CSE
    2 IT
    3 ECE

Complex Attributes : If an attribute fr an entity, is built using composite and multivalued attributes, then these attributes are called complex attributes. For example, a person can have more than one residence and each residence can have multiple phones, an addressphone for a person entity can be specified as –

{Addressphone (phone {(Area Code, Phone Number)}, Address(Sector Address (Sector Number,House Number), City, State, Pin))}

Here {} are used to enclose multivalued attributes and () are used to enclose composite attributes with comma separating individual attributes./

Key Attribute : represents primary key. (main characteristics of an entity). It is an attribute, that has distinct value for each entity/element in an entity set. For example, Roll number in a Student Entity Type.

Non Key Attributes : These are attributes other than candidate key attributes in a table. For example Firstname is a non key attribute as it does not represent the main characteristics of the entity.

Required Attribute : A required attribute is an attribute that must have a data value.These attributes are required because they describe what is important in the entity. For example, In a STUDENT entity, firstname and lastname is a required attribute.

Optional Attribute/Null Value Attribute – An optional attribute may not have a value in it and can be left blank. For example, In a STUDENT entity, Middlename or email address is an optional attribute. as some students may not have middlename or email address.

Notations Of Attributes in ER Diagram 

Attribute(Type of Attributes in DBMS) Attribute
Key Attribute-Types of Attributes in DBMS Key Attribute
Multivalued Attribute-Types of Attributes in DBMS Multivalued Attribute
Compoite Attribute-Types of Attributes in DBMS Compound/Composite Attribute
Derived Attribute-Types of Attributes in DBMS Derived Attribute

 


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