Components of the Relational Database Model

Answers and Descriptions:

1. Answer: A relation is a table in a relational database that stores data in rows and columns.
   Description: Each relation represents a specific entity (e.g., Students), with columns defining attributes (e.g., Name, ID) and rows containing data entries. Relations are the foundation of the relational model, enabling structured data storage.

2. Answer: Attributes are columns in a table that define data properties, while tuples are rows that contain actual data values.
   Description: For example, in a “Students” table, attributes might be “Name” and “Age,” while a tuple could be (“Alice”, 17). Understanding these terms is key to designing and querying relational databases.

3. Answer: A primary key constraint ensures each tuple in a table is uniquely identified by one or more attributes and cannot be null.
   Description: A primary key, like a student ID, prevents duplicate records and ensures data integrity. It is critical for uniquely identifying records and establishing relationships with other tables.

4. Answer: A foreign key constraint links a column in one table to the primary key of another, ensuring referential integrity.
   Description: For instance, a “Grades” table might have a foreign key “StudentID” referencing the “Students” table’s primary key. This ensures only valid StudentIDs are entered, maintaining consistency across tables.

5. Answer: A NOT NULL constraint ensures that a column cannot have null values, requiring a value for every tuple.
   Description: For example, a “Name” column with NOT NULL ensures every student record has a name, preventing incomplete data and ensuring data reliability for critical fields.