search
Log In

Recent questions tagged candidate-keys

1 vote
2 answers
1
Let $R=(A,B,C,D,E,F)$ be a relation scheme with the following dependencies: $C\to F,E\to a,EC\to D, A\to B$. Which of the following is a key for $R$? $CD$ $EC$ $AE$ $AC$
asked Mar 31 in Databases Lakshman Patel RJIT 136 views
0 votes
2 answers
2
0 votes
1 answer
3
If there is more than one key for relation schema in DBMS then each key in relation schema is classified as prime key super key candidate key primary key
asked Mar 31 in Databases Lakshman Patel RJIT 85 views
0 votes
6 answers
4
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
asked Mar 24 in Databases jothee 182 views
1 vote
2 answers
5
Which of the following key constraints is required for functioning of foreign key in the context relational databases? Unique key Primary key Candidate key Check key
asked Jul 2, 2019 in Databases Arjun 853 views
1 vote
1 answer
6
In relational database management, which of the following is/are property/properties of candidate key? P: Uniqueness Q: Irreducibility P only Q only Both P and Q Neither P nor Q
asked Jul 2, 2019 in Databases Arjun 640 views
1 vote
2 answers
7
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 Ram Swaroop 311 views
0 votes
0 answers
8
I've some elementary doubts regarding Foreign keys (referential integrity) : Can a foreign key consist of a collection of attributes - ie. can two or more columns collectively form a foreign key? If foreign key refers to a column within the same ... that has either: Multiple candidate keys Composite candidate keys Overlapping candidate keys If possible, please provide an example. Thank You.!
asked Nov 19, 2018 in Databases Harsh Kumar 188 views
0 votes
0 answers
9
Can Prime attribute be NULL in any of the the Candidate key ?? Can Prime attribute be NULL in Primary key ??
asked Oct 23, 2018 in Databases jatin khachane 1 56 views
0 votes
1 answer
10
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 Na462 160 views
1 vote
2 answers
11
An instance of a relational schema R(A,B,C,D) has distinct values for attribute A then A can be 1) candidate key 2)non key 3)super key 4)none
asked Sep 14, 2018 in Databases Shivani gaikawad 119 views
0 votes
0 answers
12
Referencing to this gate ques- https://gateoverflow.in/16095/gate2004_13-let-and-two-relation-schema-where-the-primary-key Let R1 (A, B, C) and R2 (D, E) be two relation schema, where the primary keys are shown underlined, and let C be a foreign key in R1 ... foreign key, subtracting entities of D from C can still have null and other values(those were duplicate). So, how will it get empty set?
asked Sep 1, 2018 in Databases bts1jimin 240 views
0 votes
1 answer
13
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 Na462 539 views
1 vote
1 answer
14
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 hacker16 514 views
0 votes
2 answers
15
0 votes
1 answer
16
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 function dependency. ... c) 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 sunil sarode 459 views
0 votes
0 answers
18
I came across a statement that says that in BCNF, a prime attribute cannot be transitively dependent on a key. But consider a relation R (A, B, C) where, A --> ABC , B --> ABC , C --> ABC Clearly it is in BCNF and each of A, B and C are candidate keys. Now A - ... > C and A --> C . Thus, we can tell C(a prime attribute) is transitively dependent on A (a candidate key) !! Where am I making mistake?
asked Nov 8, 2017 in Databases humblefool 109 views
3 votes
4 answers
19
If A Relation R(A,B,C,D) and CK given is (AB,C) and FD is given as A->C Then the relation is in which highest normal form?
asked Sep 19, 2017 in Databases Anirudh Pandey 492 views
1 vote
1 answer
20
2 votes
1 answer
21
R(A,B,C,D,E,F,G,H) A->BC B->CFH CH->G E->A A->EG what is the number of candidate key
asked Jul 25, 2017 in Databases iamHarin 268 views
0 votes
1 answer
22
A relational schema R with attributes (ABCDEFG).It is known that D never appears on RHS of any FD.How many different possibilities are there for what a Candidate key of R can be.?
asked Feb 3, 2017 in Databases Ravi_1511 182 views
0 votes
1 answer
23
Given relation R(A, B, C, D, E) and set of functional dependencies F = {AB → C, AB → D, D → A, BC → D, BC → E} Number of candidate key in the following relation have?
asked Jan 18, 2017 in Databases srestha 794 views
0 votes
1 answer
25
4 votes
3 answers
26
A relation R(A,B,C,D,E,F) holds following FDs $AB\rightarrow C$ $C\rightarrow D$ $D\rightarrow EA$ $E\rightarrow F$ $F\rightarrow B$ The number of minimal candidate keys of R are _______.
asked Oct 29, 2016 in Databases GateAspirant999 977 views
0 votes
2 answers
27
Let there be relation R(A, B, C, D, E) where candidate keys are A, BC and D. How many superkeys are possible?( Marks: 0.00 ) 26 Explanation: Answer = Number of superkeys(A) + Number of superkeys (BC) + Number of superkeys (D) - Number of superkeys (ABC) - Number of superkeys (BCD) - ... - 23 + 21 = 16 + 8 + 16 - 4 - 4 - 8 +2 = 26 28 30 32 can anyone further elaborate the formula used why 2^x?
asked Sep 28, 2016 in Databases Shashank Chandekar 228 views
7 votes
2 answers
28
Consider the following database table having A, B, C and D as its four attributes and four possible candidate keys (I, II, III and IV) for this table: A B C D $a_1$ $b_1$ $c_1$ $d_1$ $a_2$ $b_3$ $c_3$ $d_1$ $a_1$ $b_2$ $c_1$ $d_2$ ... not equal to $d_2$) then which of hte above could not be the candidate key for the database table? I nad III only III and IV only II only I only
asked Aug 16, 2016 in Databases jothee 3.8k views
...