Recent questions tagged databases - GATE CSE Doubts

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Applied Gate Database
Hi, I am kind of confused on how to proceed after finding the closures for {A, B, C, D} (Kind of using brute force to find all the required relations). Please provide in detail how you will be going to approach this.

asked 1 hour ago in Databases by badman (7 points) | 2 views

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#made-easy #database
statement:Relational calculus is equivalent to relational algebra. according to me above statement should correct but In ans it is given false.

asked 13 hours ago in Databases by 404 found (27 points) | 12 views

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#made-easy #serializability
consider the following schedule: S:W1(A) W2(B) W3(B) W4(B) The number of schedule which are view equal to s is _____. ans is 6 but i am getting 8 ans didn’t considers these two combinations: W2(B) W3(B) W4(B) W1(A) W3(B) W2(B) W4(B) W1(A) Is these two combinations can possible ?

asked 14 hours ago in Databases by 404 found (27 points) | 9 views

+2 votes

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NLCIL2020(BASIC)
Q.1)which of the following is not considered as multivalued and composite attribute. a)AADHAR NUMBER b)Date of birth c)Age d)Address

asked 2 days ago in Databases by BASANT KUMAR (25 points) | 13 views

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NiC 2020 STA SET A Q 86
Q. A minimal super key (i.e, one of the super key for which no proper subset is a super key) is called: A) SUPER KEY B) CANDIDATE KEY C) PRIMARY KEY D) BOTH CANDIDATE KEY AND PRIMARY KEY I THINK option B is correct Plz check

asked 6 days ago in Databases by Hradesh patel (5 points) | 10 views

+2 votes

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NIELIT STA (SERIES C-QUE_111)
A minimal Super key (i,e one of the super keys for which no proper subset is a super key) is called: A- Super key B- Candidate key C- Primary Key D- Both Candidate key and Primary key option D is correct as per the ans key I think option B is correct. Need valid proof/reference for the same

asked Nov 26 in Databases by Sgr007 (21 points) | 19 views

+1 vote

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NIELIT2020 Paper
Set of key attributes that identify weak entities related to some owner entity is classified as: A. Structural key B. String key C. Partial key D. Foreign key Answer given is Partial Key but I think it should be d) Foreign key. I am having this ... weak refers to the owner Primary key, So isn't the relationship therefore being defined by Foreign key btw owner & weak entity.

asked Nov 26 in Databases by Ankit Raina 7 (5 points) | 10 views

+1 vote

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NIELIT NIC scientist-B 2020 set-C ques 48
An instance of relational schema R(A,B,C) has distinct values of A including NULL values. Which one of the following is true? A is candidate key A is not a candidate key A is primary key both (a) and (c)

asked Nov 26 in Databases by ayush.5 (97 points) | 53 views

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External Sorting - Calculate number of passes
Let suppose that we have a file with n = 10^6 records. The block size is B = 10 records and we have available main memory m = 20 blocks. (Sorting with MergeSort) 1. How many runs will you produce in the ... /classes/Comp115-Spring2017/exercises/Comp115-Class13-ExSol-External-Sorting.pdf) and i am confused about the different terms i have to manage.

asked Nov 25 in Databases by AlgoHuman (5 points) | 7 views

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Mergesort - Number of compares between keys
How i can prove that the number of collisions between two keys remain the same and it is independent with the runs(count of sub-divides) that algorithm do ?

asked Nov 24 in Algorithms by AlgoHuman (5 points) | 11 views

+1 vote

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self doubt in Normalization
Why we don’t allow a prime attribute to transitively dependent on a key in BCNF but allow in 3 NF ?

asked Nov 12 in Databases by s_dr_13 (15 points) | 14 views

+1 vote

1 answer

Nested Subquery
In a nested subquery, if the inner query having an ALL operator returns NO ROWS, how come the outer query returns TRUE for all the tuples? Here is an example.

asked Nov 10 in Databases by superak96 (9 points) | 22 views

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Loop,control structure in DBMS
Write a PL/SQL code to print tables of all even numbers up to 10.

asked Nov 7 in Databases by rakhi thakur (5 points) | 14 views

+1 vote

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Trishna knowledge DBMS
Consider the given schedule with data-locks on dataitems, check whether it has dead-lock or not. The locks are shared-lock(S) and Exclusive-lock(X). Shared-lock is also called Read-lock, Exclusive-lock is also called Write-lock. Read and Write operations are denoted by R and W, ... A) Which of the following is incorrect? (A) T1 → T2 (B) T3 → T1 (C) T2 → T3 (D) T4 → T3

asked Nov 2 in Databases by anushkaaa (43 points) | 23 views

–1 vote

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database management systems
hi guys, if a lossless, dependency preserving relation is there, then it can be decomposed into 3NF if a lossless, dependency preserving relation is there, then it can be decomposed into bcnf which one is correct? and why?

asked Oct 28 in Databases by rish1602 (9 points) | 29 views

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View serialisability
While checking whether a schedule is view serialisable or not. I read that if there is no blind write then schedule is not view serialisable. I am not able to figure out reason behind this.

asked Oct 24 in Databases by vizzard110 (85 points) | 47 views

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Deriving FD's from given FD set
Suppose two FD’s are given W ->X and W->Y can we derive by replacing left hand side attribute? Are X->Y and Y->X are also valid?

asked Oct 22 in Databases by vizzard110 (85 points) | 15 views

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made-easy relational-algebra
consider the relation R(A, B, C, D). Which relational algebra expression to return the lowest value of A?

asked Oct 21 in Databases by kalin (143 points) | 25 views

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Applied gate mock 1
Whether the given schedule is serializable or not? The given schedule is clearly not conflict serializable as precedence graph contains cycle.. But will it be view serializable or not?? I used For View Equivalence: (1) If transaction Ti reads initial value of any ... satisfied.. (if you got any violation then let me know) But the given answer says it is not view serializable..

asked Oct 21 in Databases by Verma Ashish (697 points) | 21 views

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DatabaseTransaction
what is difference between blind write and write write conflict .

asked Oct 3 in Databases by muskan24r (5 points) | 43 views

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Previous Gate
https://gateoverflow.in/2510/gate1994-14 For a B+ - tree of order d with n leaf nodes, the number of nodes accessed during a search is O(−) Please explain me Sachin’s answer in extra details. I cant even understand after 2 lines.

asked Sep 11 in Databases by Gupta731 (17 points) | 20 views

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Made Easy Subject Wise DBMS
Consider the following schedule: S: r1(A), r2(A), r3(A), r4(A), w1(B), w2(B), w3(B), w4(B). Find the number of all possible view-equivalent schedules. Find the number of all possible conflict-equivalent schedules. How many serializable schedules are there that are not conflict serializable.

asked Sep 10 in Databases by Ollie (459 points) | 132 views

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Self Doubt Database recoverability
All conflict serializable schedules are recoverable.[True or False] Please provide the explanation as well as reference too if possible

asked Sep 10 in Databases by Ollie (459 points) | 71 views

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Made Easy Subject Wise Database
If a relation is in BCNF surely it will be in a 4NF as well. [True or False, with explanation] Made Easy Solution : True. [I think False]

asked Sep 9 in Databases by Ollie (459 points) | 43 views

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Made Easy DBMS
Which of the following statement is false? Relation with every attribute is prime, always in BCNF. Relation with every attribute prime always in 3NF. Relation R which satisfies 3NF and atmost one compound candidate key is also in BCNF Relation with every candidate key is ... , so as per me, Option (D) also is false, while according to Made Easy it is true, someone please clarify.

asked Sep 9 in Databases by Ollie (459 points) | 43 views

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Self Doubt on Transcation & Concurrency Control
Why this schedule is not View Serializable?? Anyone please elaborate this.

asked Sep 7 in Databases by AbhayPrajapati (7 points) | 38 views

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#self doubt #databases #normqlisation
If we decompose R(ABCDE) into 2nd normal form what all tables we get . Given FDs(A->C,C->D,D->E,C->A).

asked Sep 4 in Databases by Anujjain (7 points) | 55 views

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applied test series
The original answer says that every team participating should have exactly one refree which I think is wrong. my observations:- 1. if there is a refree then he/she needs to instruct atleast a single game 2.if there is a match btw two teams then they ... teams present that doesn't plays a match. PS-here the refree entity is in total participation please correct me if I am wrong

asked Sep 4 in Databases by Sahil91 (33 points) | 16 views

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Self Doubt - (PYQs)
https://gateoverflow.in/1485/gate1999-2-7-ugcnet-june2014-iii-25 In this question if $R_1 \cap R_2 = \phi$ then will the decomposition will be lossy but does that mean that $R_1$ and $R_2$ individually can’t be in 2NF, 3NF or BCNF?

asked Sep 2 in Databases by Mellophi (363 points) | 19 views

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Raghu Ramkrishnan - Transactions and Concurrency Control

asked Aug 30 in Databases by pritishc (23 points) | 59 views

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Made Easy Workbook
Please someone solve Q35.

asked Aug 28 in Databases by Mellophi (363 points) | 36 views

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ME TEST SERIES
Can anyone tell how this works?

asked Aug 27 in Databases by Shashank Rustagi (715 points) | 29 views

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Self doubt DBMS Conflict Equivalent schedules
$\text{Consider the transactions given below}$ What are the number of conflict equivalent schedules possible What is the approach to solve such questions T1 T2 T3 $r_{A}$ $w_{B}$ $r_{A}$ $w_{B}$ $r_{A}$ $w_{B}$

asked Aug 26 in Databases by Shashank Rustagi (715 points) | 41 views

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MADE EASY CN+DBMS TEST SERIES GATE 2020
I only II only Both None Which option is correct give justification

asked Aug 26 in Databases by Shashank Rustagi (715 points) | 25 views

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Self Doubt (Nested Loop Join)
Can someone please clarify why we keep the smaller loop outer and the bigger loop inner? (i.e. why do we select the relation with smaller number of tuples as the outer relation)

asked Aug 16 in Databases by Mellophi (363 points) | 22 views

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#DBMS #Self-Dobt
What is the maximum number of candidate keys we can have?

asked Aug 15 in Databases by munishchaturvedi (19 points) | 20 views

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#DBMS #Self-Doubt
Can phi be a super Key? In what corner cases can it be? What is the maximum number of Super Keys?

asked Aug 15 in Databases by munishchaturvedi (19 points) | 28 views

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Self-Doubt Normalization
Is Every Table with 2 single valued attribute is in 2nf, 3nf, bcnf? Why?

asked Aug 14 in Databases by munishchaturvedi (19 points) | 30 views

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Self-Doubt #DBMS #Candidate Keys
If candidate keys given are A1, A2, A3, then waht are number of super keys if we only have those n attribues in relation A1 to A?.

asked Aug 14 in Databases by mamtuj (-25 points) | 49 views

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Self-Doubt #DBMS #Index
Can anyone tell me on which fields we can define Clustering Index on? What are conditions?

asked Aug 14 in Databases by mamtuj (-25 points) | 24 views

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