Recent questions tagged functional-dependencies

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1

BCNF Decomposition

asked Jul 14 in Databases by Na462 Active (4.6k points) | 44 views

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2

Database Normal forms
Given a relation R(ABCD) with functional dependencies: $AB \to CD\\ BC \to D$ Normal form is? 1) 1 NF 2) 2 NF 3) 3 NF 4) BCNF

asked Jul 10 in Databases by cynicthnkr (109 points) | 39 views

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3

Normalization - 3NF doubt
A relation has the attributes R(ABCDEPG). The set of Functional Dependencies are : $F: { AB \to CD, DE \to P, C\to E, P\to C, B \to G }$ After normalising this relation till 3NF, I get the following tables : ${ ... A LOSSLESS AND DEPENDENCY PRESERVING PROPERTY IN 3NF - But I am not getting the Dependency Preservation property. Is something wrong with the decomposition ?

asked Jul 4 in Databases by Harsh Kumar Junior (615 points) | 60 views

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1 answer

4

Function Dependency question
Consider a relation R(A,B,C,D,E,F,H) with A as the only key. Assume that the dependencies E->F and C-> DEH hold.on R. 1. Is R in 2NF? If not, decompose to 2NF. 2. is R in 3NF? if not, decompose to 3NF. //What does " with A as the only key" mean ?

asked Jun 23 in Databases by karthikmenon (11 points) | 98 views

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5

Closure of a set of functional dependency

asked Jun 22 in Databases by Harsh Kumar Junior (615 points) | 57 views

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6

NORMALIZATION
Given: The Relation R(A,B,C,D,E) having (A,B) as Primary key. The set of functional dependencies: (A,C)-->D , (B,D)-->E. I want to Know whether the functional dependencies Given above are Partial FD's or Not?

asked Jun 8 in Databases by pradeepchaudhary (209 points) | 95 views

+2 votes

1 answer

7

Dependency Preservation
Doubts : - 1. R(A,B,C,D) and The Functional Dependencies are = AB->C, C->AD . So when I'll decompose it then it will be R1(A,B,C) and R2(C,D).We cannot do R1(A,B,C) and R2(C,A,D) because the Production C->A will ... check R1 intersection R3 as well ? because if we do then it wont be lossless as there isn't any common attribute. Please tell the right way to check.

asked Apr 22 in Databases by Na462 Active (4.6k points) | 84 views

+1 vote

1 answer

8

3NF Normalization Doubt
Is a relation with multiple candidate keys in 3NF? According to this, As per the first definition any relation having multiple candidate keys will have transitive dependency to a non key attribute. My Inference : Since it has a Transitive dependency ... given is correct or not.And if it is correct can you please provide some other reference illustrating the same concept.

asked Jan 25 in Databases by Sourajit25 Junior (825 points) | 74 views

+1 vote

1 answer

9

FD cover
F: { A-> BC, B->C, AC->B } G: { AB->C, A->B, A->C } Does G cover F?

asked Jan 19 in Databases by Tuhin Dutta Loyal (7.9k points) | 74 views

+2 votes

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10

3NF Fully functional dependent
Consider the following statements: A relation R is in 3NF, if every non-prime attribute of R, is fully functionally dependent on some key of R. State True or False

asked Jan 15 in Databases by anabee (99 points) | 184 views

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11

#candidate keys
Given a relation R{A, B, C, D, E, H} and having the following functional dependencies : {A → BC, CD → E, E → C, D → AEH, ABH → BD, DH → BC} The number of candidate keys for relation R is ________.

asked Dec 15, 2017 in Databases by Tuhin Dutta Loyal (7.9k points) | 127 views

+1 vote

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12

BCNF Normal form
R(A,B,C,D,E) AB ---> E CD ---->A B ------>C Decompose the following relation to BCNF and also state whether it is lossless and dependency preserving

asked Dec 12, 2017 in Databases by Mk Utkarsh Boss (14.1k points) | 108 views

+1 vote

1 answer

13

Functional Dependency
Validity of third statement

asked Dec 8, 2017 in Databases by Pawan Kumar 2 Active (4.5k points) | 44 views

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14

Number of Super keys
Q1) Consider the relation with n attributes if any 2 attribute is a candidate key, then the total number of candidate keys are___ ? Then what will be the generalized formula I) $\sum_{i=2}^{n}C(n,i)$ II) $\sum_{i=2}^{n}C(n,i)*C(i,2)$ ... then ABE is a single superkey. So which one is correct? Q2) Is the answer remains same if use every in place of any in above question?

asked Dec 3, 2017 in Databases by Shubhanshu Boss (15.1k points) | 163 views

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15

Dbms normalization
https://gateoverflow.in/?qa=blob&qa_blobid=11537552088967137608

asked Dec 1, 2017 in Databases by Harikesh Kumar Active (1.4k points) | 72 views

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16

Multivalued Dependency
Can anyone please explain it ?

asked Nov 30, 2017 in Databases by ankitgupta.1729 Loyal (6.6k points) | 73 views

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17

Multivalued Dependency
Can anyone please explain how to check Multivalued Dependency ?

asked Nov 30, 2017 in Databases by ankitgupta.1729 Loyal (6.6k points) | 52 views

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1 answer

18

Number of tables after decomposition

asked Nov 29, 2017 in Databases by Parshu gate Active (4.9k points) | 70 views

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19

database normalisation
consider: T1: {A11, A12, A13} - key is A11 T2: {A21, A22, A11} - key is A21 T3: {A21, A23} - key is {A21 A23} T1, T2, T3 all are in which normal form? a) 2nf b) 3nf c) BCNF FUNCTIONAL DEPENDENCIES ARE NOT MENTIONED. SO, PLEASE EXPLAIN HOW TO CHECK NORMAL FORM FOR THE RELATION?

asked Nov 24, 2017 in Databases by iarnav Loyal (7.9k points) | 139 views

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2 answers

20

self doubt
relation schema with no non trivial fd's then relation is always in bcnf. please someone explain this i am not able to get it.

asked Nov 23, 2017 in Databases by arch Active (3.2k points) | 38 views

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1 answer

21

Match the following:
Match the following: List - I 1.Determinants 2.Candidate key 3.Non - redundancy 4.Functional dependency List - II A. No attribute can be added B. Uniquely identified a row C. A constraint between two attribute D. Group of attributes on the left hand side of arrow of ... 3 4 1 2 d) 4 3 2 1 Ans b) how Non - redundancy and Uniquely identified a row are related ? Thanks :)

asked Nov 20, 2017 in Databases by sunil sarode Active (1.3k points) | 169 views

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22

2NF decomposition
How is it option D??

asked Nov 20, 2017 in Databases by Parshu gate Active (4.9k points) | 367 views

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23

dbms question

asked Nov 19, 2017 in Databases by nikkey123 Active (1.5k points) | 116 views

+1 vote

2 answers

24

made easy test series
If a table $R$ has only one candidate key, then which of the following is always true? $R$ is in 2NF, but is not in 3NF If $R$ is in 3NF, it is also in BCNF $R$ is in 2NF, but may not be in 3NF None of these

asked Nov 10, 2017 in Databases by himanshu19 Junior (767 points) | 99 views

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25

Please solve this Q
Question: 6 Given the following functional dependencies {X → W, X → Y, Y → Z, Z → PQ} Consider the FD set implied using above FD set. Implied FD set = {X → Z, X → WY, X → WZ, X → YQ, Y → P} The number of functional dependencies in implied FD set are invalid are _________.

asked Nov 10, 2017 in Databases by kallu singh Junior (793 points) | 118 views

+1 vote

1 answer

26

ugc net November 2017
Consider a Schema R(A,B,C,D) ad the following Functional Dependencies- A→B B→ C C→D D→B The decomposition of R into R1(A,B), R2(B,C), and R3(B,D) is Dependency preserving and lossless join. lossless join but not Dependency preserving. Dependency preserving but not lossless join. Not Dependency preserving and not lossless join.

asked Nov 8, 2017 in Databases by iarnav Loyal (7.9k points) | 451 views

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27

Database doubt
Why B or B+ tree is prefer for database indexing rather than AVL tree ????

asked Oct 28, 2017 in Databases by air1ankit Active (3.5k points) | 51 views

+1 vote

1 answer

28

Doubt Database
How to remove extraneous attributes ?? Que - find the minimal cover of the functional dependency set A->BCDEF BC->ADEF B->F D->E explain whlole procedure please

asked Oct 27, 2017 in Databases by air1ankit Active (3.5k points) | 95 views

+1 vote

2 answers

29

Dbms #self doubt
1. How many super key is possible if (a,bc,cd) is candidate key and R(ABCDEF) #DOUBT When we use veen digram why we are taking only intersections part only ??? Need help please explain ..

asked Oct 26, 2017 in Databases by air1ankit Active (3.5k points) | 127 views

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1 answer

30

partial dependency

asked Oct 25, 2017 in Databases by set2018 Loyal (7.8k points) | 71 views

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