Recent questions tagged superkeys

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Made Easy Test Series:Database-Super-Keys
Consider the relation $R\left ( A,B,C,D,E \right )$ $A\rightarrow BC$ $C\rightarrow E$ $B\rightarrow D$ $E\rightarrow A$ Total number of superkeys present in relation will be ____________________

asked May 9, 2019 in Databases by srestha Veteran (119k points) | 176 views

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1 answer

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Made easy mock test 1 DBMS super keys
Consider the following relation R(A1, A2,...A15) with (A1,A2, ... A6) of relation R are simple candidate key. The number of possible superkey in relation R is_

asked Jan 30, 2019 in Databases by Ram Swaroop Loyal (5.3k points) | 201 views

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1 answer

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Self Doubt
Consider the following relation: R (A1, A2, ….An) and every (n-2) attributes of R forms a candidate key. How many super keys are there in R?

asked Jan 22, 2019 in Databases by kumar.dilip Active (5.2k points) | 115 views

+3 votes

1 answer

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MadeEasy Test Series: Databases - Functional Dependencies
Consider the relation R(A,B,C,D,E) with the functional dependencies : A → B, B → C, C → A, D → E, and E → D The Maximum possible super-keys of R is ______________?

asked Dec 7, 2018 in Databases by naveen bhatt Junior (751 points) | 197 views

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1 answer

5

Super Keys
How many Super keys Possible for R(A,B,C,D,E) with 1. {A,BC,DE} as the keys ? 2. {A,BC,CDE} as the keys ?

asked Oct 13, 2018 in Databases by Na462 Loyal (7k points) | 99 views

0 votes

1 answer

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MadeEasy Test Series: Databases - Candidate Keys
Relation R(A1, A2, A3 ..... An) n attributes. On this relation m simple candidate key (m ≤ n). How many super keys possible in this relation? A. 2m – 1 B. (2n – 1) ⋅ 2n-m C. 2n – 1 D. (2m – 1) 2n-m One way is by taking instances and solve it, but plz without it what's the logic behind the answer?

asked May 17, 2018 in Databases by Na462 Loyal (7k points) | 292 views

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2 answers

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Super Key 1
Consider the following relational schema R(ABCDE). The number of super keys in relation R if every two attributes of relation R is candidate keys are __________. Please explain a general method to solve

asked May 12, 2018 in Databases by Na462 Loyal (7k points) | 97 views

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Databases - Superkeys
How to calculate super key of any relation? Pls explain with example.

asked Apr 8, 2018 in Databases by Dhoomketu (139 points) | 94 views

+1 vote

1 answer

9

No of Super Key
R (A1, A2, ….An) and every (n-2) attributes of R forms a candidate key. How many super keys are there in R? a) $_{n-2}^{n}\textrm{C}$ b) $_{n-2}^{n}\textrm{C}$ * 4 c) $_{n-2}^{n}\textrm{C}$ * n d) $_{n-2}^{n}\textrm{C}$ + n +1

asked Jan 18, 2018 in Databases by hacker16 Active (2.7k points) | 260 views

+2 votes

0 answers

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No. of Super keys
a relation R(A,B,C,D,E,F,G,H) and set of functional dependencies are {CH->G,A->BC,B->CFH,E->A,F->EG } then how many possible super keys are present ? https://gateoverflow.in/42238/to-calculate-how-many-no-of-super-keys Is my approach right? ... BDE,BDF, EDF,AED,ADEF,ABDE,AFBE,AFBD,ABDEF}= 15 ways total = 15* 8 = 120 ways ....Can someone plz confirm it.... thank u

asked Jan 12, 2018 in Databases by Pawan Kumar 2 Active (4.2k points) | 214 views

+2 votes

3 answers

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functional dependency
Let the relation R(X, Y, Z, A, B) with given functional dependencies X -> YZ Z -> A A -> B AZ -> X The number of super keys possible__________ ? Please answer with an explanation.

asked Aug 29, 2017 in Databases by Warlock lord Active (3.3k points) | 147 views

+5 votes

2 answers

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MadeEasy Test Series: Databases - Super Keys
Consider a relation $R$ with $2n$ attributes. Assume any $2n/2$ of the attributes constitutes key. Total number of super keys possible are: $^{2n}C_{2^{n-1}}\times \left(2\right)^{2^{n-1}}$ $^{2n}C_{2^{n-1}} + \left(2\right)^{2^{n-1}}$ $^{2n}C_{2^{n-1}} - \left(2\right)^{2^{n-1}}$ $^{2n}C_{2^{n-1}} \div \left(2\right)^{2^{n-1}}$

asked Jan 18, 2016 in Databases by Tushar Shinde Active (2.2k points) | 366 views

+2 votes

1 answer

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TestBook Test Series: Databases - Super Keys
I think here even with Ph is removed from table we still get 12 Super keys. Because Salary & One of CK must be there.

asked Jan 15, 2016 in Databases by Akash Kanase Boss (41.9k points) | 152 views

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