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Differences between Super Key and Candidate Key


As a part of the database management system, maintaining the integrity of data and the ability to find things quickly are two key areas in which the practice of keys stands out. As the two categories of keys are super keys and candidate keys, the each is essential due to different reasons in a database scheme. Knowing about their differences would help us in developing database structures that are strong and can be used constantly. In this exploration, the complexities of the super keys and candidate keys are explored under the following two sections: their meaning, essence, and practical relevance.

Defining Super Keys and Candidate Keys:

To comprehend the disparity between super keys and candidate keys, it's essential to describe their definitions:

Super Key: The super key consists of a group of elements within one relation (table) which enable a distinction of each insertion (row) of that table based on the unique values of these elements. It includes the super key of the candidate key and all attributes because they are also a part of a super key. While it could be an effective way to provide unity, it could potentially be extra that can be simply avoided by having additional characteristics.

Candidate Key: On the other hand a candidate key is a minimal super key which means that the other attribute not included in it. Candidate's keys are one of the choices that could act as primary keys for a relation, which would be without any repetitions and describe each row/tuple uniquely.

Following are the tabular differences between Super Key vs Candidate Key:

Differences between Super Key and Candidate Key
Super Key Candidate Key
A super key is an attribute, or collection of attributes, that is used to identify each attribute in a relation in a unique way. A super key's subset is called a candidate key.
The combination of many super keys forms the selection criterion for the candidate keys. The criteria for choosing the primary keys is made up of a variety of candidate keys.
NULL values can be present in super key attributes. NULL values may also be present in candidate key attributes.
Not every super key has to be a candidate key. However, every candidate key is a super key.
The number of super keys in a relation is more than the number of candidate keys. In a relationship, there are fewer candidate keys than super keys.


The key sets have distinct characteristics, including uniqueness, minimality, and primary key candidates. Super keys ensure originality of tuples but may contain repetitive attributes. Candidate keys provide the most precise set of attributes, distinguishing the singleton's identity. Super keys may be used as building blocks for identifying distinct key values, but updating them becomes more complex as data is processed. Candidate keys are chosen based on simplicity and stability.


Super and candidate keys are crucial in database management systems that are dedicated to ensuring data integrity by avoiding repetition and defining key attributes for primary keys. They have the capability to accomplish the task of identifying each tuple easily. These help queries working in an organized and efficient way, and always give a well-structured schema.


Super keys, together with Candidate keys are the two main types of keys in databases. Superkeys may be made of other elements in addition to the ones necessary for unique identification, thus, assuring uniqueness while duplicating some characters. They offer flexibility of designer and can be used anywhere like in Student Management. Primary key is sample of the candidate keys that exhibit no redundancies and do not appear more than once in a single relation, therefore reducing unnecessary data elements to put it to use as a primary key for a relation.


The main types of keys in the Database management System are superkey and candidate key. Super keys are resembling general-purpose identifiers with the extra redundancies, while candidate keys are ultra-minimalistic subsets that distinguish one key from others without any redundancies. These factors shape the process of database design, managing, and performance. In addition, super keys allow flexibility in designing your schema; however, this flexibility involves some reshuffling of values to eliminate repeated attributes. By figuring out these keys' specific features, the basis for a highly accurate information structure with static operations could be established, and enhanced performance could be achieved. Knowing these concepts enables database practitioners to effectively manage data and adapt to different requirements which helps in business or technology.

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