Thursday, 7 September 2017

Descriptive attribute or Relationship attribute in Entity Relationship Model

Descriptive attribute in ER model, Relationship attribute in Entity Relationship Model, Descriptive attribute in ER diagram, Purpose of descriptive attribute, Descriptive attribute example


Descriptive attribute in ER model


The attribute(s) used for describing the relationship is called descriptive attributes, also referred as relationship attributes. They are actually used for storing information about the relationship. A relationship can have zero or more attributes.
Let us consider an example ER diagram given below;


Here, the entity sets CUSTOMER and ACCOUNT are connected using a relationship set ACCESS. A customer can have many accounts and in turn an account may belong to one or more customers. Hence, it is a many-to-many relationship.
A customer accesses his/her account to withdraw or transfer funds. And, we would like to store the information LAD (Last Accessed Date) of all accounts to keep track of recent manipulation of any account. We have included LAD as an attribute of relationship set. LAD is called as descriptive attribute/relationship attribute associated with the many-to-many relationship ACCESS.

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Go to Some keywords and Definitions in DBMS page

Go to Entity Relationship model page

Go to Reduce/Convert ER diagram to relation page







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