What’s a candidate key?

A candidate key is what is known as an “attribute” in advanced management information systems. It is a very important part of many online and computer-based datasets and is often one of the main ways that separate accounts, divisions or functions are technically differentiated. Understanding exactly how this key works requires some technical experience. In its most basic sense, however, it is a set of codes in a table that leads to a definite function that allows different branches, or “candidates,” of a common digital root to maintain separate identities, at least as far as recognition of the computer.

Basic context

In relational database management systems terms, a candidate key is an attribute used to uniquely identify a database row entry within a table. A relational database management system is a type of database that is widely used to create collections of information organized according to the provision of relationships between different elements within the database table. Similarly, a key is a tool for identifying entities. Each table can have one or more candidate keys and one of these is usually set as the primary key. The primary key is a column that defines all rows.

Almost every type of digitized database uses this type of key based system to function. Large databases such as online banking applications, scanned library files, and Internet-based email systems are some of the more obvious places to find code-based keys in action, but they operate almost constantly in most computer functions. Personal computers also often use this type of algorithm to store information on a hard drive or to create backup copies. These and most other internal processes happen silently and quickly behind the screen and behind the scenes, and people without technical knowledge often have no idea they’re running.

Relationship to the Superkey

In most cases, a candidate key is a subset of something called a “superkey”. A superkey is a type of identifier that links to an entity in a database table. Taking a corporate setting as an example, a superkey could be a column labeled VEND_CODE, which would indicate a specific vendor code for a corporate database table. The minimum number of columns needed to make each row unique is the part of the superkey that might also count as a candidate key type. In this case, if each VEND_CODE is unique, it could be the key.
Code fields
Whenever there is a field of codes, individual identifiers could function as both candidate and primary keys. In this context, the goal of each is usually to make sure that a database has no redundant rows, that is, each row contains something that makes it unique. It is important that the creator of the database choose something unique to that table when he chooses the key to be the candidate. As with the corporate database example above, you can use a company name as the key. If several companies, perhaps located in different countries, have the same name, however, that identifier would not be unique and consequently could not be used in a database that both companies could be trying to access at the same time.
Importance of a unique key
Choosing a unique candidate key is very important. Companies may share the same name, and people who are looking to open things like accounts or profiles often have the same or similar first and last names. By having the unique key and making one of them a primary key, it is easier to find a particular vendor or person via a unique key. Sometimes known names or word codes can be assigned by human technicians, but computer-generated numerical models will work as well. When each entry in the table has a key that makes it unique, it is possible to distinguish between entries that contain similar information. The system then works quickly and efficiently, which is the goal in most cases.

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