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Converting E-R model into relational model

A given ER model can be converted into Relational model. A Relational model includes Relations, Tuples, Attributes, Keys, and Foreign keys.

  • Relation is a table made from tuples.

  • A Tuple is a row of data.

  • An Attribute is a characteristic of the relation.

There is a direct mapping between ER model and Relational model.

Consider the following example −

Converting E-R model into relational model

Rules of converting ER model to Relational Model-

  • Entity type is converted to a Relation table.

  • 1:1 or 1: N relationship type is converted to foreign key.

  • M: N relationship type is converted to a relation with two foreign key.

  • Simple attribute converted to an attribute.

  • Value set converted to a domain.

  • Key attribute converted to a primary key.

Now for the above example we can create three relations-

  • Employee

  • Works_On

  • Projects

Transform attributes to fields-

  • Employee will have E_ID, Name, Designation and Dob.

  • Works_On will have E_ID, Status and P_ID.

  • Projects will have P_ID, S_Date and E_Date.

Now we can create tables in DBMS.

Overall transformation summary is −

Converting E-R model into relational model