Question

Which of the following statements about primary keys in a Relational Database Management System is true?

• A. A primary key must always be numeric
• B. A primary key can contain NULL values
• C. A primary key can contain multiple columns
• D. A primary key is used only for joining multiple tables

Answer 1

Answer:

C. A primary key can contain multiple columns

A primary key in a relational database management system (RDBMS) is a column or set of columns that uniquely identifies each row in a table. A primary key is essential for the operations of an RDBMS, and it has many benefits, including : 

• Identifying unique data: A primary key ensures that each row in a table has a unique value. 
• Preventing duplicate records: A primary key prevents duplicate records from being entered into a table. 
• Setting up relationships between tables: A primary key can be used to implement relationships between tables in a database. 
• Ensuring fields aren't null: A primary key ensures that fields in a table aren't left empty. 
• Updating or deleting specific records: A primary key can be used to update or delete specific records in a table. 
• Ensuring row-level accessibility: A primary key ensures that each row in a table is accessible.