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 integritybetween
the two tables.
E.
Create three tables, Employee, Project, and Manager.
Explanation:
Answer B, C, D, and
AWhile 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.
