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Questions tagged [candidate-key]

A key is a set of attributes that is irreducibly unique and non-nullable within a table. Irreducible means that all the attributes of the key are necessary to guarantee uniqueness - remove any one attribute and the uniqueness property would be lost. A key may consist of zero, one or more attributes and a relational table (relation variable) must have at least one key and may have more than one.

A key is a set of attributes that is irreducibly unique and non-nullable within a table. Irreducible means that all the attributes of the key are necessary to guarantee uniqueness - remove any one attribute and the uniqueness property would be lost. A key may consist of zero, one or more attributes and a relational table (relation variable) must have at least one key and may have more than one.

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How to find the candidate key by having a set of functional dependencies?

Consider relation R = (A, B, C, D, E, F) and a set of functional dependencies: AB --> C BC --> A BC --> D D --> E CF --> B What are all the candidate keys? Please if anyone can give me the answer and explain how.
user2974935
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Database candidate keys from functional dependencies - specific technicality

I am working with a relational database's set of attributes and set of functional dependencies and have a specific question about which keys would be considered candidate keys of this schema. The set of attributes I am working with is: R = (A, B, C,…
user1462294
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What is the best way to choose primary key in candidate key?

I am concerned about which candidate key to select as the primary key among the candidate keys. Assume that using mysql database(innoDB). Suppose we have a unique value, Student Number, and a unique value, ID Number(eg Social Security…
rabong
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Primary Key vs Candidate Key - Relational DBMS

My understanding is that the primary key is a randomly chosen candidate key from a theoretical perspective. According to this definition ' Candidate Key – A Candidate Key can be any column or a combination of columns that can qualify as unique…
Daniel
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Confusion re PK (primary key) and CK (candidate key) for FDs (functional dependencies) in R={A,B,C,D,E,F}

I have a confusion re the question below since according to me maybe its answer is that AD is a candidate key. But it is the primary key so I want to know: Is its candidate key the same as its primary key? A relation R={A,B,C,D,E,F} is given with…
Bhavya
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Functional dependency: find candidate key

In relation R = (ABCDEFGH) the set of functional dependencies that hold is {BE -> GH, G -> FA, D -> C, F -> B} What is a candidate key of R? I found the answer can be BED, DEG, or FED. However, this question is a multiple choice question where I…
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Find the functional dependencies and candidate key

In the relation X below P, Q, R, S, T and U are the attributes of the relation. Find the functional dependencies and candidate keys. Relation X +---+---+---+---+---+---+ | P | Q | R | S | T | U | +---+---+---+---+---+---+ | p | c | e | i | k | v…
user3588341
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