CODEWITHSUNDEEP
mysqlrelational-databaseentity-relationship
J.Alzaibak
J.Alzaibak

Reputation: 31

What is the different between Attributes in Entity Diagrams and Attributes in Relations.

In the The Entity Relationship Diagram (ERD), Columns are attributes that belong to the entity modeled by the table.

But what is the different between these attributes in Entity Diagrams and Attributes in Relations in Database.

Upvotes: 0

Views: 711

Answers (1)

reaanb
reaanb

Reputation: 10065

Attributes in the ER model are mappings from entity sets or relationship sets to value sets. That means non-key ER attributes are represented by a key/value column pair in a physical model/database, not just a single column.

Attributes in the relational model correspond with roles in the predicate of the relation (key or not). These are generally represented by individual columns, but the components of a logical relation need not correspond one-to-one with the elements of a physical model. A logical date could be represented by 3 int columns. A set of true/false attributes could be represented as a single bit field.

Upvotes: 1

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