Alternate Key

Definition of Alternate Key

In database management, an alternate key is a secondary unique identifier for a record, used to retrieve data when the primary key is unavailable or unsuitable. It is a column or set of columns that possess the unique constraint property, ensuring that no two records within the table have the same values. By offering multiple access points to specific data, alternate keys enhance data retrieval efficiency and maintain data integrity.


The phonetic pronunciation of “Alternate Key” is:/ˈɔːltərnət kiː/Here’s a breakdown:Alternate – ˈɔːltərnət (aw-l – tuhr – nuht)Key – kiː (kee)

Key Takeaways

  1. An Alternate Key is a secondary unique identifier for a row in a database table, used when the Primary Key is not appropriate or sufficient for certain operations.
  2. Alternate Keys help in maintaining data integrity, ensuring that no two rows have the same values for the designated key columns, preventing duplicate records.
  3. They provide additional options for building relationships between tables in a database, increasing query performance, and enhancing database structure flexibility.

Importance of Alternate Key

The term “Alternate Key” holds significance in technology because it represents a critical concept in database management and data organization.

An alternate key is an attribute or a combination of attributes in a database table that uniquely identifies each row or record, serving as an alternative to the primary key.

By providing a secondary means of ensuring data integrity, alternate keys help prevent duplicate entries and maintain consistency within the database.

Additionally, they enable users to retrieve, filter, or sort data more efficiently, reinforcing the versatility and reliability of databases in managing vast amounts of information.

Overall, the importance of alternate keys lies in their essential role in supporting effective and accurate data storage and retrieval in database management systems.


Alternate keys play a vital role in managing and organizing complex databases, ensuring data integrity and efficient data processing. The primary purpose of an alternate key is to provide a secondary means of uniquely identifying records within a database table. While primary keys serve as the primary means of identifying records, they might not always capture other unique attributes which hold significant value in the database.

Alternate keys come into play in such scenarios, allowing users to look up records through additional columns that contain unique values other than the primary key. This is particularly useful when dealing with large datasets, where multiple attributes are required to effectively distinguish between records, and aid in speeding up search queries. Furthermore, alternate keys facilitate the establishment of relationships between different database tables.

By acting as foreign keys to reference records in other related tables, they contribute to the creation and maintenance of referential integrity. This aids in avoiding the duplication of data, leading to a more structured, organized and manageable database system. In essence, alternate keys serve to enhance the overall efficiency of database management, while streamlining data querying and information retrieval processes, ensuring that relational databases remain robust and reliable over time.

Examples of Alternate Key

Alternate keys are essential in database management systems for uniquely identifying records within a table, providing an alternative to primary keys. Here are three real-world examples of alternate key usage:

Banking System: In a customer database, the primary key for each user’s record may be a “Customer ID.” However, banks can also use the user’s Social Security Number (in the US), or other unique identification numbers like the Tax Identification Number as alternate keys. These keys provide an additional way to look up and validate customers during transactions, ensuring accurate data management.

Human Resources Management System: An organization’s HR department maintains employee data, consisting of unique employee IDs as primary keys. They can use alternate keys, such as email addresses, to maintain unique identification of each employee. This allows the HR system to find or verify employees via multiple data points, which can be especially helpful during onboarding or employee verification processes.

E-commerce Platforms: In an online shopping platform, the primary key for each customer may be a “User ID.” E-commerce platforms can use the customer’s email address or registered phone number as alternate keys to avoid duplicate accounts based on the same individual. Additionally, alternate keys help to validate user information and ensure the communications are correctly sent to appropriate customers.

Alternate Key FAQ

What is an alternate key?

An alternate key is a set of one or more attributes in a database table that can uniquely identify a specific record. It is an alternative to the primary key and provides another option for ensuring data integrity and avoiding duplicate records.

Why are alternate keys used?

Alternate keys are used because they offer additional ways to enforce uniqueness in a database. They also ensure data integrity by preventing duplicate records. In some cases, an alternate key may be more user-friendly or provide better performance than a primary key.

What is the difference between an alternate key and a primary key?

A primary key is a column or set of columns in a database table that uniquely identify each row in the table. An alternate key, on the other hand, is an alternative way of uniquely identifying a specific record in a table. Alternate keys can have null values, while primary keys cannot.

How do I create an alternate key in a relational database?

To create an alternate key in a relational database, you must first identify a column or set of columns that can uniquely identify each row. Then, you need to add a UNIQUE constraint to these columns to enforce uniqueness. The specific syntax for creating an alternate key depends on the database management system you are using.

Can a table have multiple alternate keys?

Yes, a table can have multiple alternate keys. Each alternate key must enforce uniqueness in a different set of columns, providing various ways of uniquely identifying records in the table.

What is the role of alternate keys in normalization?

Alternate keys play an important role in database normalization, specifically in the process of creating relations in third normal form (3NF). In 3NF, relations should only have columns that are dependent on the primary key. Alternate keys can be used to identify columns that are candidate keys and should be separated into new relations to maintain normalization.

Related Technology Terms

  • Database normalization
  • Primary key
  • Unique constraint
  • Indexing
  • Foreign key

Sources for More Information


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