Recent questions and answers in Databases - GATE CSE Doubts

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ISI 2019 PCB
Let R be a relation with functional dependencies F. For any subset of attributes $X ⊆ R$, the closure of $X$ is defined as the set $X^+$ = {$A ∈ R$ | $X → A$ holds with respect to $F$ }. For two non-empty attribute sets $Y$ and $Z$ in $R$, prove or disprove each of the following statements: (a) $(Y^+Z)^+ = (Y Z)^+$ (b) $(YZ)^+ = Y^+Z^+$

asked 10 hours ago in Databases by thebiggercypher (6 points) | 1 view

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GATE CSE 2014 PREVIOUS YEAR QUESTIONS
Consider a join (relation algebra) between relations r(R)r(R) and s(S)s(S) using the nested loop method. There are 3 buffers each of size equal to disk block size, out of which one buffer is reserved for intermediate results. Assuming size(r(R))<size(s(S)) , ... s(S)s(S) is more than 0.5. join selection factor between r(R)r(R) and s(S)s(S) is less than 0.5 [closed]

asked 1 day ago in Databases by Setika Mehra (9 points) | 7 views

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made easy, postal package, database management system, ch1

asked Mar 15 in Databases by Setika Mehra (9 points) | 8 views

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Made easy, postal package, database management system

asked Mar 15 in Databases by Setika Mehra (9 points) | 4 views

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CIL MT EXAM 2020
The _______ defines a set of operations on relations, paralleling the usual algebraic operations such as addition, subtraction or multiplication, which operate on numbers. A.Refrential integrity B.Relational algebra C.Relations D.Relational calculus What should be answer?. Given answer is B.

answered Mar 8 in Databases by !KARAN (351 points) | 31 views

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DBMS Doubts 1
In general if any two precedence graphs of two schedules are isomorphic does that mean they are conflict equivalent?

answered Mar 7 in Databases by Kushagra गुप्ता (261 points) | 20 views

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1 answer

CIL MT EXAM 2020
A ______ is the combination of one or more column values in a table that make a row of data unique within the table. A.primary key B.foreign key C.candidate key D.natural key given answer is a but why c is not correct . please answer so that we will challenge it.

answered Mar 6 in Databases by rjking7403 (27 points) | 28 views

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Madeeasy Workbook DBMS
Given a system using unspanned blocking and 100 byte blocks. A file contains record of 20,50,35,70,40,20. what percentage of space will be wasted in the blocks allocated for the file?

answered Mar 5 in Databases by smsubham (64 points) | 21 views

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1 answer

Asked in NST-2
If all attributes of relation are prime attribute, then the relation is always in 3NF True/False?

answered Mar 2 in Databases by Kushagra गुप्ता (261 points) | 25 views

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2 answers

Schedules DBMS
Consider the following statements: 1.Conflict serializability testing condiions are both necessary and sufficient for serializability testing. 2.View serializability testing condiions are both necessary and sufficient for serializability testing. 3.If a Schedule(S) is not conflict serializable ... the following are incorrect? 1 and 3 2 and 3 1 and 2 1,2 and 3 Anyone please clarify.

answered Feb 27 in Databases by Abhisheksmile94 (25 points) | 44 views

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Made Easy test series dbms maximum number of candidate key

answered Feb 27 in Databases by Abhisheksmile94 (25 points) | 29 views

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1 answer

Self Doubt Transactions DBMS
Explain too.

answered Feb 27 in Databases by Abhisheksmile94 (25 points) | 26 views

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korth - database concept - clustering index
why it is not possible in general to have two clustering indices on the same relation for different search keys?

asked Feb 26 in Databases by Abhisheksmile94 (25 points) | 10 views

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Database concept by korth exercise 2.3
Consider the time slot relation. Given that a particular time slot can meet more than once in a week, explain why day and start time are part of the primary key of this relation, while end time is not.

asked Feb 19 in Databases by Abhisheksmile94 (25 points) | 10 views

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SELF DOUBT: CONSERVATIVE 2PL
Can $conservative$ $2PL$ be $NON-RECOVERABLE?$ according to me they can be, but in some places i find them to be mentioned as recoverable.. which is true?

asked Feb 5 in Databases by Debapaul (699 points) | 36 views

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Btree and B+tree deletion (selfdoubt)
I am not able to do B tree and B+ tree deletion properly. If anyone can suggest some resource I would really be grateful.

asked Feb 3 in Databases by Pratyush Priyam Kuan (804 points) | 17 views

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1 answer

TRANSACTIONS AND CONCURRENCY CONTROL GATE 2017-2marks

answered Feb 2 in Databases by kashyap02 (26 points) | 29 views

+1 vote

1 answer

ACE- FLT:DBMS
Should * be right associative here?plz check

answered Feb 1 in Databases by shashin (1.9k points) | 21 views

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1 answer

ACE FLT:DBMS
How D could be correct ans here, Plz verify

answered Feb 1 in Databases by shashin (1.9k points) | 26 views

+1 vote

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DBMS Two-phase locking self-doubt.
I've made this table out of my own understanding. Please help me fill in the question marks, and also verify other entries if possible. Simple 2PL Conservative 2PL Strict 2PL Rigorous 2PL Deadlock possible? $✓$ $\times$ $✓$ $✓$ ... does it produce recoverable/cascadeless schedules? If yes, why; if no, why? Sources to your answers would be much appreciated.

asked Jan 28 in Databases by JashanArora (7 points) | 70 views

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Databases Normalization
Can someone explain the last option If R in 3NF and not in BCNF then R must have atleast two compound candidate keys – TRUE / FALSE.

asked Jan 27 in Databases by kashyap02 (26 points) | 21 views

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Self Doubt- DBMS
In which cases is a schedule view serializable but not conflict serializable? Please show with an example.

asked Jan 27 in Databases by Mellophi (7 points) | 19 views

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made easy testseries DB
How to solve this question?

asked Jan 25 in Databases by Dheeraj Varma (22 points) | 21 views

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Self Doubt: Normalization
“If a relation is in 3NF but not in BCNF then it must have atleast 2 compound candidate keys.” Is it true or false? I remember reading somewhere on GO that a relation is in 3NF but not in BCNF only when there are overlapping candidate keys. Above statement is from ME CBT 2 where they’ve given it false.

asked Jan 23 in Databases by Sambhrant Maurya (401 points) | 28 views

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declare an integrity constraint
The text belo is from C J date's database book . Why it would be unreasonable to declare an integrity constraint to that effect ? Correctness: By definition, the database is always at least in a consistent state where, following ... assume that transactions are correct, in the sense that they faithfully reflect just those real-world operations they are supposed to.

asked Jan 23 in Databases by Tara22 (6 points) | 7 views

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Dbms self doubt
Given the statement- View Serializable testing conditions are both necessary and sufficient conditions for serializability testing", whether it is correct or not? please explain.

asked Jan 23 in Databases by SuvasishDutta (209 points) | 52 views

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Self doubt : Applied Test DBMS
Question. Given: serach key = 9 bytes, Record pointer = 6bytes Block pointer = 5 bytes, Block size = 512 bytes Every block is 69% full . My Approach: 5n + (9+6)(n-1) <= 69% *(512) 5n + 15n - 15 <= 353.28 20n <= 368.28 n <= 18.41 n = 18. n is order if B tree. keys per node = n-1= 17.

asked Jan 22 in Databases by tp21 (269 points) | 25 views

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Applied course mock test locking protocols

asked Jan 21 in Databases by Vignaneswarkrishna (14 points) | 12 views

+2 votes

1 answer

Made easy test series : Normalization
if every candidate key of R is simple candidate key and no non trivial functional dependency like non-prime attribute-->other non-prime attribute exists then R also in BCNF. Whether the above given statement is true or false?

answered Jan 21 in Databases by tp21 (269 points) | 48 views

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1 answer

ISRO 2020 Database
If every non-key attribute functionally dependant on the primary key, then the relation will be in (a) First normal form (b) Second normal form (c) Third normal form (d) Fourth normal form

answered Jan 21 in Databases by vivek07 (9 points) | 55 views

+1 vote

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Self Doubt: Min no of tables in recursive(unary) relationships

asked Jan 20 in Databases by Sambhrant Maurya (401 points) | 13 views

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Made easy test series : SQL
Consider the following relations: Which of the following query gives suppliers names who have submitted at least one Harvest' brand item? (sno in item is the foreign key referencing sno in supplier). I. Select sname FROM Supplier S, Item t where t.brand ... S where sno IN (Select sno FROM Item where brand = Harvest') What will be the correct answer for above question?

answered Jan 20 in Databases by godfather (9 points) | 24 views

+1 vote

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Self doubt : Serializability Dbms
We know that a schedule even if it is not conflict nor view serializable still it can be consistent and there is no typical method to find them. So my doubt is that Such schedules which are neither view serializable nor conflict serializable but consistent can be termed as serializable??

asked Jan 20 in Databases by Chirag Shilwant (180 points) | 50 views

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applied gate:b-tree

asked Jan 20 in Databases by abhinav649 (67 points) | 8 views

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applied gate mock:dbms
given the SQL quey: SELECT * FROM A WHERE A.T1 NOT IN (SELECT B.T3 FROM B) Number of tuples returned by the above SQL query is:

asked Jan 19 in Databases by abhinav649 (67 points) | 27 views

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GATE MOCK TEST 3 GATE 2019 Q32 DBMS
Is there any trickfor solving such questions quickly. It wasted a lot of time still I couldn’t get it right

asked Jan 18 in Databases by DukeThunders (415 points) | 17 views

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#Self_doubt#Database_NaturalJoin
After doing R natural join S the table will have A,B,C attributes so on natural join of this table with Table T do we need to compare A and C both or only A or C?

asked Jan 17 in Databases by nandani17 (33 points) | 12 views

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MadeEasyTest
I think answer should be 13 (17-4=13) anyone plz confirm

asked Jan 17 in Databases by nandani17 (33 points) | 16 views

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ace testseries full length test
53.

asked Jan 17 in Databases by Rahul Burman (21 points) | 17 views

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Self Doubt: Adding attributes/relations to BCNF to convert it into dependency preserving

asked Jan 17 in Databases by shashin (1.9k points) | 25 views

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