Ch. 4-problem 3: Given the business rule “an employee may have many degrees,” discuss its effect on attributes, entities, and relationships. (Hint: Remember what a multivalued attribute is and how it might be implemented.) Suppose that an employee has the following degrees: BA, BS, and MBA. These degrees could be stored in a single string as a multivalued attribute named EMP_DEGREE in an EMPLOYEE table such as the one shown next: EMP_NUM EMP_LNAME EMP_DEGREE 123 Carter AA, BBA 124 O’Shanski BBA, MBA, Ph.D. 125 Jones AS 126 Ortez BS, MS
Concepts in Designing Database
A database design is the process of data organization based on a database model. The process deals with identifying what data should be stored in a database and how data elements relate to each other.
Entity Relationship Diagram
Complex real-world applications call for large volumes of data. Therefore, it is necessary to build a great database to store data safely and coherently. The ER data model aids in the process of database design. It helps outline the structure of an organization’s database by understanding the real-world interactions of objects related to the data. For example, if a school is tasked to store student information, then analyzing the correlation between the students, subjects, and teachers would help identify how the data needs to be stored.
Ch. 4-problem 3: Given the business rule “an employee may have many degrees,” discuss its effect on attributes, entities, and relationships. (Hint: Remember what a multivalued attribute is and how it might be implemented.)
Suppose that an employee has the following degrees: BA, BS, and MBA. These degrees could be stored in a single string as a multivalued attribute named EMP_DEGREE in an EMPLOYEE table such as the one shown next:
|
EMP_NUM |
EMP_LNAME |
EMP_DEGREE |
|
123 |
Carter |
AA, BBA |
|
124 |
O’Shanski |
BBA, MBA, Ph.D. |
|
125 |
Jones |
AS |
|
126 |
Ortez |
BS, MS |
Ch. 4-problem 4: What is a composite entity, and when is it used?
Ch. 4-problem 5: Suppose you are working within the framework of the conceptual model in Figure Q4.5.
Figure Q4.5 The Conceptual Model for Question 5
Given the conceptual model in Figure Q4.5:
- Write the business rules that are reflected in it.
- Identify all of the cardinalities.
Ch. 4-problem 6: What is a recursive relationship? Given an example.
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