How to multi-valued attribute in E-R diagram?

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 How do represent an multi-valued attribute in E-R diagram? How can we transfer or any attribute into our relational design?

Multi-valued attribute can be represented by double dotted ovals in an ER Diagram.
Following are the rules to follow for transformation of multi-valued attribute into relational model:

  1. An Entity type with a multivalued attribute is transformed into two relations
  2. One relation contains the entity type and other simple attributes whereas the second relation has the multivalued attribute. In this way only single atomic value is stored against every attribute.
  3. The primary key of the second relation is also the primary key of the second relation. So, in the second relation the primary key is the combination of two attributes.
  4. All values are accessed through reference of the primary key that also serves as foreign key.

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