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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 −
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 −
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