Recent questions tagged candidate-key

Consider $R(A,B,C,D)$ with $F=\{AB \to C,\ BC \to D,\ CD \to A,\ AD \to B,\ C \to BD\}$.Which of the following statements are correct?$C$ is a candidate key. $D$ is a can...

Consider $R(A,B,C,D,E)$ with $A \to B,$ $BC \to E,$ and $ED \to A$.Which of the following statements are correct?$ACD$ is a candidate key. $BCD$ is a candidate key. $CDE$...

Consider $R(A,B,C,D,E,F)$ with $AC \to B,$ $BD \to F,$ and $F \to CE$.Which functional dependency causes $R$ to violate $\text{3NF}$?$AC \to B$ $BD \to F$ $F \to C$ $F \t...

Consider $R(A,B,C,D,E)$ with $C \to D,$ $DE \to B,$ and $AB \to C$.Which of the following statements are correct?$ABE$ is a candidate key. $ACE$ is a candidate key. $ADE$...

Consider $R(A,B,C,D)$ with functional dependencies $AB \to C,$ $BC \to D$.Which statement correctly explains why $R$ is not in $\textbf{3NF}$?$AB \to C$ violates $\text{3...

Consider the relation $R(A,B,C,D,E)$ with functional dependencies $AB \to C$, $E \to D$.Assume that no other non-trivial functional dependencies hold and that all attribu...

Consider the relation $R(V,W,X,Y,Z)$ with functional dependencies :$V \to X$$WY \to X$$VWY \to Z$The candidate key is $VWY$.Assume that all attributes contain atomic valu...

Consider the relation schema $R(A,B,C,E,F,G,H)$ with $F=\{A \to BC,\ C \to FG,\ E \to HG,\ G \to A\}$Which of the following statements are correct?$A^+=\{A,B,C,F,G\}$ $A ...

Consider the relation schema $R(A,B,C,D,E)$ with$F=\{AB \to C,\ CD \to E,\ DE \to B\}$Which attributes must necessarily occur in every candidate key of $R$?$A$ $B$ $C$ $D...

Consider the relation$Student(S,I,E,N,L)$with the functional dependencies$F=\{S \to I,\ I \to E,\ E \to S,\ N \to L\}$Which of the following are candidate keys?$SN$ $IN$ ...

Consider the relation schema $R(A,B,C,D,E,F)$ with$F=\{BE \to C,\ B \to F,\ D \to F,\ AEF \to B,\ A \to E\}$Which of the following is a candidate key of $R$?$ACD$ $AD$ $F...

Let $K_1$ and $K_2$ be two distinct candidate keys of a relation $R$.Let $S_1$ and $S_2$ be two superkeys of $R$.Which of the following statements are always true?$K_1\cu...

A relation schema $R$ has $6$ attributes.What is the maximum number of candidate keys that $R$ can simultaneously have?

Consider the following relation instance $R(A,B,C)$:$$\begin{array}{|c|c|c|}\hlineA & B & C \\\hline\alpha & \delta & \xi \\\beta & \delta & \psi \\\gamma & \eta & \xi \\...

Let $\text{R(A, B, C, D, E)}$ be a relational schema with functional dependency set $\mathrm{F}=\{\mathrm{A} \rightarrow \mathrm{BC}, \mathrm{CD} \rightarrow \mathrm{E}, ...

Let $R$ be a relation schema with a set of functional dependencies $F$.The relation $R$ is decomposed into $n$ relation schemas$R_1, R_2, \ldots, R_n$.Consider the follow...

Can a super key contain NULL values?If yes, please explain why it is allowed.If not, please explain why NULL values are not permitted in a super key.Also, can a candidate...

Do the following exist for EMPTY instances?Super KeyCandidate KeyPrimary KeyIf yes, could anyone please elaborate?

An alternate key in database table is also calledPrimary keyCandidate keySuper keyForeign key

Consider a relation schema $\mathrm{R}=(\mathrm{U}, \mathrm{V}, \mathrm{W}, \mathrm{X}, \mathrm{Y}, \mathrm{Z})$, on which the following functional dependencies hold:$$\{...

A superkey for an entity consists of :one attribute onlyat least two attributesat most two attributesone or more attributes

The correct answer is a and d. I just wanted to know that why not b and c. It is possible that it may be speed and color is also a candidate key. If you have any clarific...