You work as a Database Designer for SoftTech Inc. You have developed the conceptual design of the
database of an organization. Following is the ER-diagram, which you have designed. Now you have
to convert the following diagram to a logical model.
Which of the following steps will you take to accomplish the task?
Each correct answer represents a part of the solution. Choose all that apply.
A.
Now migrate the Start Date attribute of “works on” relationship to the Project table.
B.
Create two tables, Employee and Project.
C.
Create a primary key for both the tables.
D.
Migrate the primary key of the Employee table to the Project table to maintain referential
integrity between the two tables.
E.
Create three tables, Employee, Project, and Manager.
Explanation:
While converting the conceptual model to a logical model, the following steps are to be followed:
Convert the entities defined in the ER-diagram to tables. The attributes of entities are represented
as columns in the table. In the above mentioned ER-diagram, there will be two tables, Employee and
Project. Define the primary keys for both the tables, EmpID for the Employee table and ProjectID for
the Project table.Migrate EmpID, i.e. the primary key of the Employee table, to the Project table to
maintain referential integrity constraint between the two tables.Migrate the attribute Start Date of
the “works on” relationship in the same direction as the primary key, i.e. in Project table.
The process is shown below as a logical diagram:Note: The relational model does not support “relationship” data structure like the hierarchical
model; therefore, the information that was defined in the relationship attribute should be migrated
to an existing or associative entity. The Start Date attribute of “works on” relationshipis therefore
migrated to the Project table.
