Question

Design a relational database containing information about students, their courses, and their current semester along with their disciplines. (Avoid redundancies similar to those in Figure 9.4.)

Short answer

Create tables for Student, Course, Semester, and Discipline with appropriate foreign keys and normalize data.

Step-by-step solution

Identify Entities

In the given scenario, the entities are 'Student', 'Course', 'Semester', and 'Discipline'. Each of these will form the main tables in our database as they represent the key components of the system.

Define Attributes for Each Entity

For each entity identified, we need to specify attributes. 'Student' might have attributes such as 'StudentID', 'Name', 'Email'. 'Course' would include 'CourseID', 'CourseName', and 'Credits'. 'Semester' might have 'SemesterID' and 'SemesterName'. 'Discipline' could have 'DisciplineID' and 'DisciplineName'.

Determine Entity Relationships

Students enroll in Courses, so there is a many-to-many relationship between 'Student' and 'Course'. This implies a join table (e.g., 'Enrollment') featuring 'StudentID' and 'CourseID'. Similarly, students have disciplines, so another table might be 'StudentDiscipline' containing 'StudentID' and 'DisciplineID'.

Define Foreign Keys

In the join tables ('Enrollment' and 'StudentDiscipline'), you will use 'StudentID' and 'CourseID' in 'Enrollment', and 'StudentID' and 'DisciplineID' in 'StudentDiscipline' as foreign keys to maintain referential integrity.

Eliminate Redundancy and Ensure Normalization

Ensure tables are in 3rd Normal Form (3NF) by only storing attributes that are fully functional depending on the primary key. For instance, course details should not be stored in the 'Student' table, minimizing redundancy.

Key concepts

Entities and Attributes

When we talk about a relational database, the concepts of "Entities and Attributes" are fundamental. An entity refers to any object or concept that holds some data. In our student database scenario, entities include "Student", "Course", "Semester", and "Discipline". These entities form the foundation of our database design.

Each entity is described by a set of attributes. These attributes represent the properties that an entity possesses. For instance, the "Student" entity may have attributes like "StudentID", "Name", and "Email". Similarly, a "Course" could have attributes like "CourseID", "CourseName", and "Credits".

Attributes are crucial because they define what data will be stored for an entity. Choosing meaningful attributes ensures that the database captures each entity's necessary information without excess or missing data. The deliberately designed attributes help maintain data accuracy and efficiency in queries.

• Example: Every student in our database will have a unique "StudentID" to maintain distinct records.

Entity Relationships

Entity relationships describe how entities in our database relate to one another. Understanding these relationships is vital for creating an accurate database schema.

In the student database example, consider that students enroll in various courses. This identifies a many-to-many relationship between "Student" and "Course" entities. A straightforward way to handle such relationships is through a join table, in this case, named "Enrollment". This table will typically include primary keys from both entities involved.

A similar relationship occurs between "Student" and "Discipline". Students may choose multiple disciplines, indicating another many-to-many connection. Here, we can again create a join table, perhaps called "StudentDiscipline".

Modeling these relationships accurately ensures that our database can efficiently manage and retrieve related data.

• Example: Each entry in the "Enrollment" table ties a "StudentID" with a "CourseID", representing a specific student's registration in a course.

Foreign Keys

Foreign keys are an essential component of relational databases, providing a mechanism to maintain referential integrity between tables.

In our database design, foreign keys help link related tables. For instance, the join tables "Enrollment" and "StudentDiscipline" use foreign keys to associate records with the "Student", "Course", and "Discipline" tables.

Consider the "Enrollment" table, which includes the attributes "StudentID" and "CourseID". Here, "StudentID" serves as a foreign key referencing the "Student" table, and "CourseID" as a foreign key referencing the "Course" table. This setup ensures that every entry in "Enrollment" corresponds to existing students and courses, preventing errors such as linking to non-existent records.

Foreign keys thus enable databases to enforce rules about the validity of the relationships they model, helping maintain data consistency across tables.

• Example: A student enrolling in a course must have valid "StudentID" and "CourseID" values present in their respective tables.

Normalization

Normalization is a critical process in designing a relational database. It involves organizing database tables to minimize redundancy and dependency. The goal is to reduce data repetition and improve data integrity.

Normalization is achieved through a series of rules called normal forms, with the 3rd Normal Form (3NF) being a common level of normalization. At this stage, a table's attributes depend only on the primary key, and there are no transitive dependencies.

For the student database, ensuring normalization involves creating tables in which each attribute is functionally dependent on its primary key. For example, details about a course should solely reside in the "Course" table, preventing the need to store course information in the "Student" table, and thus avoiding redundancy.

• A benefit of normalization is that it leads to a more structured and efficient database design, simplifying data updates and maintenance tasks.

Student Database Schema

Designing a "Student Database Schema" requires a clear understanding of entities, their relationships, and how to apply normalization principles.

The schema begins by defining tables for each identified entity—"Student", "Course", "Semester", and "Discipline". For each table, include necessary attributes like primary keys to uniquely identify records. This structured design allows the database to efficiently store and retrieve information.

Next, establish relationships between tables using join tables, such as "Enrollment" for "Student"-to-"Course" relationships and "StudentDiscipline" for "Student"-to-"Discipline" connections. These join tables often consist mainly of foreign keys.

Ensuring that the schema adheres to normalization rules helps eliminate data redundancy and maintains data integrity. By doing so, the schema supports accurate queries and supports future database scaling or modifications effectively.

• The schema serves as a blueprint for implementing the database, guiding systematic data management and access.