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Super key in dbms8/24/2023 Find the value of K such that the number of candidate keys must be maximum.Ĭhoosing K values from N is done by NC K.įor the above value, K = N/2 for maximum. In relation, a number of super keys is more than a number of candidate keys. All super keys can’t be candidate keys but the reverse is true. ![]() ![]() Thus, a super key is the superset of a key known as a Candidate key (discussed in the next section). DBMS Difference between Super Key and Candidate Key MKS075 Read Discuss Super Key: Super Key is an attribute (or set of attributes) that is used to uniquely identifies all attributes in a relation. The word super denotes the superiority of a key. Suppose we have a relational model with attributes as and there is one candidate key made with K attributes. We can define a super key as a set of those keys that identify a row or a tuple uniquely. We will count the number of super keys present in a relational model (table) by understanding various examples, which are discussed below:Ī UNION B UNION C = A + B + C - (A INTERSECTION B) - (B INTERSECTION C) - (C INTERSECTION A) + (A INTERSECTION B INTERSECTION C) Each primary key or candidate key is a super key, but each super key cannot be called a candidate key. Often DBMS beginners get confused between super key and candidate key, so we will also discuss candidate key and its relation with super key in this article. The super key is the super subset of the primary key or candidate key. Definition of Super Key in DBMS: A super key is a set of one or more attributes (columns), which can uniquely identify a row in a table. In DBMS, a set of attributes used to identify each row uniquely is called a super key. ![]() Candidate key: A minimal (irreducible) superkey. Next → ← prev Number of Possible Super Keys in DBMS Super Key Superkey: An attribute (or a combination of attributes) that uniquely identifies each row in a table.
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