Consider the case of an organization having many departments. Each department has a department head
known as senior manager. Several employees are working in a department under the senior manager. Identify
the most appropriate ER-diagram that represents therelationship between department and employees.
Answer:
Explanation:
The relationship between department and employees is one-to-many and that of employees and department is
one-to-one, i.e. an employee
can work in only one department at a time.
In the figure, a single line across the right end of the relationship represents one-to-one cardinality. The
crowfoot at the left end of the relationship signifies an optional cardinality of any number of, or several.
Answer C is incorrect. A single line across the left end of the relationship represents one-to-one cardinality. The
crowfoot at the right
end of the relationship signifies an optional cardinality of any number of, or several. According to this figure, an
employee can work in several
departments and a department has a single employee,which is not possible. Answer B is incorrect. A single
line between the two entities means one-to-one cardinality. Answer A is incorrect. A single line across the left
end of the relationship represents one-to-one cardinality. However, in this case, a
department can have several employees, not just one.