If you belong to the world of Data Management Systems (DBMS), then knowing An Alternate Key is essential. In DBMS keys play a crucial role in uniquely identifying a record within a table and a table in a database represents a collection of records or events that is for a particular relation.

In today’s world, the concept of DBMS is highly in demand since it allows organizations to properly manage, access, and safeguard their data, thereby facilitating better decision-making, business operations, and creativity.


So here is a complete guide to understanding What is An Alternate key in DBMS with real-world examples.

What is An Alternate Key in DBMS?

What is An Alternate key in DBMS?

An Alternate Key or secondary key is certainly the key that contains all the properties of the candidate key but is an alternate option. Therefore, An Alternate Key is a column or a group of columns capable of identifying a unique record within the table. 

However, the primary key still stands as a candidate key. It uniquely identifies a record that is different from the primary key in a table. It is also a candidate key which means it satisfies all the uniqueness guidelines.

Hence, Only one key candidate key can be chosen as the primary key so the rest of the candidate’s keys automatically become alternative keys. You can learn Data Analytics Skills by taking some professional Data Science courses.

The importance of An Alternate Key in DBMS

The main motive for creating Key is to give each record a unique identity. There are broadly seven types of Keys in which An Alternate Key in DBMS is an alternative way to distinguish between one record from another within a table.

What is An Alternate Key in DBMS

So, for using an Alternate Key with its full potential let’s have a look at the key reasons them the Alternate Keys have such great significance in DBMS.

To Improve the Integrity of the Data

Alternate keys can also be used not only to enforce uniqueness but also to ensure that duplicates or similar records are not entered thereby maintaining data integrity.

Querying and Retrieving of Data

 An alternate key can be used for querying a table or joining two tables as an alternative to primary keys. Thus, it is easier to have multiple tables joined based on specific fields such as employees and departments.

Natural Data Representation

As it is based on natural attributes like the email addresses of customers or the stock-keeping unit (SKU) of a product therefore it can give a meaningful identification of records.

Integration with External Systems

When databases must be merged with others or applications, they provide a default key for matching transactions and actions.

Adapting to Business Logic

Real-world business scenarios may demand unique identifiers rather than the primary key. With the help of Alternate keys data management, can be more approachable and likewise align with specific business requirements.

Characteristics of Alternate Key

In the DBMS ecosystem, the essential characteristics of Alternate Keys must be understood. So Let’s overview them.

Principle of uniqueness

Just like the primary key, the alternate key must have uniqueness so that it can singularly identify each unique record across the table. So the real purpose of Alternate Key lies in the insurance of such kind of uniqueness.

Non-Null constraint

Just like, the primary key the alternative key also enforces a uniqueness-Null) constraint. T As a result it prevents duplicate values from being updated or inserted within each record of the table.

Candidate Key

However, due to specific considerations, the alternate key may not have chosen a candidate key but it has all the potential to be a candidate key. That is to say, if the need arises the alternate key can easily function as a candidate key.

A Few Example of Alternate Key

Moreover, you can get a strong grip on this topic by joining the Best Data Science Courses in India. But let’s have some more clarity on what is An Alternate Key in DBMS by discussing some examples here.

Example 1:

Let’s Consider there is an EMPLOYEE_DETAIL table where the following attributes are given to us

Emp_SSN: The specific attribute stores employees’ SSN (social security number)

Emp_Id: In this attribute, the values of the employee identification number are stored.

Emp_name: With the specific employee ID that attribute also stores the name of the employees.

Emp_email: The email IDs of each employee are stored in this Emp_email attribute.

Hence, from the given table we can observe that Emp_SSN, Emp_ID, and Emp_email are the candidates Key. Emp_name can not be the candidate key because more than one person in the same company can have the same name. 

Emp_SSN Emp_IDEmp_name      Emp_email
11021 01Raj[email protected]
1102202Neha[email protected]
1102303  Preeti[email protected]
1102404Dipak[email protected]
  Candidate Keys

Furthermore, after finding the candidate keys, now we will have to find the most appropriate Key to become the primary key. So from the observation, we can conclude that Emp_SSN is the primary key and the rest of the two, Emp_ID and Emp_email are the Alternative Keys.

Example 2:

Furthermore, in the next example, attributes about Student_Detail are provided.

Stud_roll_no: The attribute provides a unique identification number for each student.

Stud_name: This attribute is for storing the names of the students along with the specified roll numbers.

Stud_email: The email ID of the particular student is given in this attribute, along with the specified roll number.

Stud_Course: The attribute holds the information about the course taken by the particular student along with the specified roll number.

Let’s overview the Student_Detail table that is shown below:

Stud_roll_no  Stud_name    Stud_email    Stud_course
[email protected]
[email protected]
[email protected]
[email protected]

Therefore, from the table, we can conclude that stud_roll_no is the most appropriate option for setting as a Primary Key. Thus, the remaining identified keys will be the candidate keys, which will be considered alternate keys.

What Is An Alternate Key in DBMS- Learn from the Experts

If you want to upgrade your skills with the latest AI trend to unfold limitless career opportunities We would highly recommend Henery Harvin which is one of the largest online learning platforms. Indeed they provide futuristic career skills, and in addition, it offer Data Analytics Training courses. These courses will not only help you to learn concepts deeply but also prepare you for the evolving demands. You can understand the basics and gain practical experience by enrolling in Henry Harvin’s internships. Henry Harvin has a vast range of courses in various fields that are in demand nowadays such as  Data Science,  Content writing, Cloud computing, and many more.


Hence, in the end, we can say that an alternate key is not only a secondary player but a key player in the database management system that is designed to, ensure that the data retrieval and management can be done together. In this way, if we continue to upscale our understanding of DBMS, then the significance of the alternate key is essential for creating databases.

Recommended Reads

  1. Data Analytics Salary In India For Freshers In 2024
  2. What Is a Data Warehouse And How It Works?
  3. Top 20 Data Analysis Tools in 2024
  4. Top 15 Most Important Python Features You Should Know


Ques 1-  What are the benefits of using an Alternate Key in DBMS?

 Ans- Alternate Key in DBMS is very useful as it provides an Alternative way to uniquely identify the records. It can help search and organize data within the database. Along that, an Alternate key can also consist of one or multiple columns and helps to ensure data integrity and efficient data retrieval within the database.

Ques 2- How is an Alternate Key different from a Primary Key?

Ans- The Primary Key is the Key that is chosen to uniquely identify the records in the table without any Null value. On the other hand, an alternate Key is the candidate key that has been selected as an addition so that it could serve as a unique identifier.

Ques 3- Can an attribute containing Alternative Key have NULL values?

Ans- No, An Alternative Key is like the primary Key so it should not have a NULL value. Despite that, It must have the NON-NULL value for each unique record to ensure its effectiveness.

Ques 4- How can an Alternate Key be indexed in DBMS?

Ans- In DBMS An Alternate Key can be indexed in the same indexing mechanism as used for the primary Key.

Ques 5 How Alternate Keys are useful in Data dividing or sharding?

Ans- The goal of dividing or sharding data by using Alternate Keys is not only to distribute data across multiple physicals but also logical partitions in DBMS. Therefore, By dividing data into smaller parts the performance and availability can be increased.

E&ICT IIT Guwahati Best Data Science Program

Ranks Amongst Top #5 Upskilling Courses of all time in 2021 by India Today

View Course

Recommended videos for you

Join the Discussion

Interested in Henry Harvin Blog?
Get Course Membership Worth Rs 6000/-
For Free

Our Career Advisor will give you a call shortly

Someone from India

Just purchased a course

1 minutes ago
Henry Harvin Student's Reviews
Henry Harvin Reviews on Trustpilot | Henry Harvin Reviews on Ambitionbox |
Henry Harvin Reviews on Glassdoor| Henry Harvin Reviews on Coursereport