Question 3 - Past Year - 2 Mark Questions - Chapter 8 - Database Concepts

Last updated at April 16, 2024 by

Differentiate between the primary key and alternate key of a table with the help of an example.

 

Answer:

  • Primary key refers to a set of one or more attributes which can uniquely identify tuples in a relation. 
  • Alternate key refers to any candidate key which is not selected as the primary key.

Example:

Employee_id

Employee_name

Department

Emp_Email

101

Ravi Kumar

Sales

ravi1@gmail.com

102

Tarun A

IT

ta121@gmail.com

103

Jennifer Davis

HR

jenny@gmail.com

104

Martin Woods

HR

martin@gmail.com

105

Ron Romy

IT

roro@gmail.com

 

In table employee, the candidate keys are Employee_id and Emp_Email since we can uniquely identify an employee with either of the two.

If we select Employee_id as the primary key, then Emp_Email becomes an alternate key. 

Transcript

Differentiate between the primary key and alternate key of a table with the help of an example. Answer: Primary key refers to a set of one or more attributes which can uniquely identify tuples in a relation. Alternate key refers to any candidate key which is not selected as the primary key. Example: Employee_id Employee_name Department Emp_Email 101 Ravi Kumar Sales ravi1@gmail.com 102 Tarun A IT ta121@gmail.com 103 Jennifer Davis HR jenny@gmail.com 104 Martin Woods HR martin@gmail.com 105 Ron Romy IT roro@gmail.com In table employee, the candidate keys are Employee_id and Emp_Email since we can uniquely identify an employee with either of the two. If we select Employee_id as the primary key, then Emp_Email becomes an alternate key.

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