# Recent questions tagged database-normalization

1
Which one of the following statements are not correct? $S1$: $3$NF decomposition is always lossless join and dependency preserving. $S2$: $3$NF decomposition is always lossless join but may or may not be dependency preserving. $S3$: BCNF decomposition is always lossless join and dependency ... but may or may not be dependency preserving. Only $S1$ Only $S4$ Both $S1$ and $S4$ Both $S2$ and $S3$
1 vote
2
Which of the following is TRUE? Every relation in $3$NF is also in BCNF A relation R is in $3$NF if every non-prime attribute of R is fully functionally dependent on every key of R Every relation in BCNF is also in $3$NF No relation can be in both BCNF and $3$NF.
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Consider the relational schema $R(A B C D)$ with following $FD$ set $F=\{A \to CE, B \to D, AE \to D\}$. Identify the highest normal form satisfied by the relation $R$. $2$NF BCNF $3$NF $1$NF
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Consider the relational schema $\text{R(A B C D)}$ with following functional dependency set $F=\{A\rightarrow BC,C\rightarrow D\};$ The relation $\text{R}$ is in $2$NF BCNF $3$NF $1$NF
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Which one is correct w.r.t. RDBMS? primary key $\subseteq$ super key $\subseteq$ candidate key primary key $\subseteq$ candidate key $\subseteq$ super key super key $\subseteq$ candidate key $\subseteq$ primary key super key $\subseteq$ primary key $\subseteq$ candidate key
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For database relation $R(A,B,C,D)$ where the domains of $A,B,C$ and $D$ include only atomic values, only the following functional dependencies and those that can be inferred from them are: $A \rightarrow C$ $B \rightarrow D$ The relation $R$ is in First ... well as in second normal form Second normal form but not in third normal form. Both in second normal form as well as in third normal form.
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If every non-key attribute functionally dependent on the primary key, then the relation will be in First normal form Second normal form Third normal form Fourth Normal form
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The multivalued dependencies (MVDs) can be eliminated using ______ normal form on _____ normal form relations. $1$st, $2$nd $2$nd, $3$rd $3$rd, BCNF $4$th, BCNF
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In relational databases, if relation R is in BCNF, then which of the following is true about relation R? R is in 4NF R is not in 1NF R is in 2NF and not in 3NF R is in 2NF and 3NF
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In a relation, if every attribute is prime but key may not be simple then the relation is in ______. A. 1NF B. 2NF C. 3NF D. BCNF
1 vote
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Consider the relation $R\left ( A,B,C,D,E \right )$ with functional dependencies $F=${ $A\rightarrow B$ $BC\rightarrow E$ $ED\rightarrow A$ } Number of additional relation required to convert it into lossless , dependency preserving $3NF$ decomposition is _____________ What is meaning of additional relation (Here no table mentioned previously)??
12
Consider the following relational schemes: R(A, B, C, D, E, F) and S(A, B, C) with in the following functional dependencies: I. AB --> C II. C --> ABDE III. ADE --> F Assume {A,B} is the key for both schemes. Which of the following statements is true? R ... : only AB→ C is the relation for the S table, which satisfies BCNF properties. (So S is in BCNF) Please let me know if it is correct or not.
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Consider a relation $R\left ( A,B,C,D,E \right )$ and functional dependencies are $F=\left \{ AC\rightarrow B,C\rightarrow D,A\rightarrow E,C\rightarrow B \right \}$ Relation $R$ is decomposed into $R_{1}\left ( A,B,C \right )$ and $R_{2}\left ( C,D \right )$ Then Is it a lossless decomposition? I am getting doubt, how it can be not lossless decomposition?
14
Decompose into BCNF R(A, B, C, D, E) FD: AB->C, C->D, D>B, D->E
1 vote
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Do we need to find closure of functional dependencies of original relation to check whether the decomposed tables are in 2NF . I know that we have to do the above process for 3NF and BCNF . If yes , please give a example where we need to do it
17
Consider 2 tables R1 and R2 . If we perform a cross product between them the condition that should be satisfied for not generating spurious tuples is both should have a common element which should be a 1>primary key 2>candidate key 3>super key In one of the tables which of the three is correct??
18
Consider a relation $R (A, B, C, D, E, F, G, H)$ where each attribute is atomic, and following functional dependencies exist. Following relation is in $1 NF,$ I help me to decompose relation into $BCNF$ $CH\rightarrow G$ $A\rightarrow BC$ $B\rightarrow CFH$ $E \rightarrow A$ $F\rightarrow EG$
19
Let the set of functional dependencies $F=\{QR \rightarrow S, \: R \rightarrow P, \: S \rightarrow Q \}$ hold on a relation schema $X=(PQRS)$. $X$ is not in BCNF. Suppose $X$ is decomposed into two schemas $Y$ and $Z$, where $Y=(PR)$ and $Z=(QRS)$ ... $Y$ and $Z$ is dependency preserving and lossless Which of the above statements is/are correct? Both I and II I only II only Neither I nor II
20
S: If a relation R is in 3NF but not in BCNF then relation R must consist atleast 2 overlapped candidate keys. True/False
21
Find the highest normal form. AB - - > CE E - - >AB C-->D Doubt AB, E are the candidate key. The answer given is 2NF In 2NF, there should be no partial dependency which is PRIME ATTRIBUTE - - >NON PRIME ATTRIBUTE But it is there in AB-->CE, I think CE is non prime attribute. Or bcoz of E we consider them as prime attribute.
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Select the ‘False’ statement from the following statements about Normal Forms: 1. BCNF is stronger than 3NF 2. Lossless preserving decomposition into BCNF is always possible 3. ​​​​​​​ Any Relation with two attributes is in BCNF 4. Lossless preserving decomposition into 3NF is always possible
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Are 3NF decompostions and BCNF decompostions unique? Are 4NF important for GATE (since I've left them :( ) See, I am asking this question because I want to know whether they'll ask about no. of tables we get after normalizing upto 3nf or bcnf. Now, if the decompostions are ... question or not I am in a bit hurry to search for that.. so please forgive me if it has been already asked.) Thank you.
26
Consider the schema R = (S T U V) and the dependencies S → T, T → U, U → V and V → S. Let R = (R1 and R2) be a decomposition such that R1 ∩ R2 = ϕ. (In the actual gate question it was R1∩R2 ≠ ϕ) The decomposition is:- not in 2NF in 2NF but not 3NF in 3NF but not in 2NF in both 2NF and 3NF
27
A3 also deriving {A1,A2,A3} from FD’s...why it is still neglecting BCNF? Is solution wrong or I am misunderstanding?
Can someone explain the paragraph marked based on relation $r$ given in Figure 7.2? Reference: Database System Concepts by Silberschatz, Korth, Sudarshan 4th Edition. ​​​​​