Question

Consider the following relations for a database that keeps track of student enrollment in courses and the books adopted for each course: sTuDENT(SSN, Name, Major, Bdate) COURSE(Course#, Cname, Dept) ENROLL(SSN, Course#, Quarter, Grade) BOOK_ADOPTION(Course#, Quarter, Book_ISBN) TEXT(Book ISBN, BooLTitle, Publisher, Author) Specify the foreign keys for this schema, stating any assumptions you make.

Short answer

The foreign keys are as follow: ENROLL(SSN) references STUDENT(SSN), ENROLL(Course#) references COURSE(Course#), BOOK_ADOPTION(Course#) references COURSE(Course#), and BOOK_ADOPTION(Book_ISBN) references TEXT(Book_ISBN). In BOOK_ADOPTION, Quarter might also associate with Quarter in ENROLL, but it's ambiguous without more context.

Step-by-step solution

Identify Primary Keys

First determine the primary keys for each table. Presumably, these are: SSN for STUDENT, Course# for COURSE, a combination of (SSN, Course#, Quarter) for ENROLL, combination of (Course#, Quarter, Book_ISBN) for BOOK_ADOPTION, and Book_ISBN for TEXT.

Set Foreign Keys for ENROLL

ENROLL table links STUDENT and COURSE. Here, SSN is a foreign key referencing STUDENT(SSN), and Course# is a foreign key referencing COURSE(Course#).

Set Foreign Keys for BOOK_ADOPTION

BOOK_ADOPTION table connects COURSE with TEXT. So, Course# is a foreign key referencing COURSE(Course#) and Book_ISBN is a foreign key referencing TEXT(Book_ISBN). Also, it's important to notice that Quarter in BOOK_ADOPTION references Quarter in ENROLL.

Key concepts

Primary Keys

Primary keys are a cornerstone in the design of relational databases. They are unique identifiers for each record in a database table. No two records within the same table can have the same primary key value, which ensures that each record is unique and can be retrieved or related to without ambiguity.

To put this into perspective using the example provided, each student is assigned a unique Social Security Number (SSN), which serves as their primary key within the STUDENT table. Similarly, each course has a unique Course Number (Course#) in the COURSE table. When a primary key consists of more than one column, like in the ENROLL table, where it's a combination of SSN, Course#, and Quarter, it's referred to as a composite key. These keys not only ensure record uniqueness across multiple columns but also create a link between tables, often serving as a cornerstone for foreign key relationships.

Understanding primary keys is crucial as they not only help in identifying records with precision but also act as a reference point for foreign key relationships within the database schema.

Foreign Keys

Foreign keys act as a bridge between tables in a relational database. They are columns in one table that reference the primary key columns of another table. This is not just a conceptual link; foreign keys enforce referential integrity, ensuring that the relationships between data are consistent and the database remains free of orphan records, which are entries that don't have a corresponding link in another table.

In our example, the ENROLL table contains foreign keys such as SSN and Course#, which link back to the STUDENT and COURSE tables, respectively, by referencing their primary keys. The foreign key constraints ensure that you cannot have an enrollment record for a non-existent student or course. Identifying and setting up foreign keys properly is a crucial task in database schema design as they are essential for relational data models. They enable complex queries across multiple tables, enforcing data integrity and making the database robust and reliable.

Relational Database

A relational database is an organized collection of data points with pre-defined relationships between them. These databases are structured in a way that recognizes relations among stored items of information. This is achieved through the use of tables which represent different entities. Each table has columns (attributes) and rows (records), and the intersecting point of a column and a row holds the actual data value.

The beauty of a relational database lies in its ability to efficiently retrieve and manipulate these data points in relation to one another. This is done through primary and foreign keys which establish connections between different datasets. For instance, in the provided schema, the BOOK_ADOPTION table relates to the COURSE table through the Course# (foreign key), which allows one to quickly find which books have been adopted for a particular course.

Understanding the core structure and principles of a relational database is invaluable for anyone designing or working with data systems. This knowledge forms the foundation for creating databases that are both flexible and have the integrity required to handle complex data relationships.