Recent questions tagged databases - GATE CSE Doubts

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Self Doubt regarding ER diagram
What is degree of Self Referential Relationship? Unary or Binary?

asked 1 day ago in Databases by adas7099 (9 points) | 5 views

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Made easy self dought
Q. R(A,B,C,D,E,F) with {A,BC,CD} candidate keys.How many super keys possible?

asked 2 days ago in Databases by Enolx.21 (49 points) | 26 views

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How to convert this problem statement to ER model
Can Somebody know how to design ER Diagram from this ?

asked 4 days ago in Databases by ghostman23111 (5 points) | 6 views

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Gate 2020 question
Consider a database implemented using B+ tree for file indexing and installed on a disk drive with block size of 4 KB. The size of search key is 12 bytes and the size of tree/disk pointer is 8 bytes. Assume that the database has one million ... each record fits into one disk block. The minimum number of disk accesses required to retrieve any record in the database is ______.

asked Feb 13 in Databases by Enolx.21 (49 points) | 12 views

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Made easy test
In this question, it is asked to retrieve the name of each employee who has a dependent with the same first name and is the same sex as employee. How Q1 will give the correct result, coz inside IN() the condition Essn=D,Essn is not there. Can anybody explain.

asked Feb 6 in Databases by Ankita87077 (11 points) | 22 views

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Made easy test series
Consider the following table: A B C a1 b1 c1 a1 b1 c2 a2 b1 c1 a2 b1 c3 Number of non-trivial functional dependencies exists in the above Table ___________.

asked Feb 4 in Databases by vikashrajpoot0100 (5 points) | 19 views

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self doubt Databases : What do partial dependencies really mean ?

asked Feb 2 in Databases by ashutoshbsathe (5 points) | 12 views

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Self Doubt , Databases
Is Read – Write conflict possible in a strict recoverable schedule? As strict 2PL guarantees strict recoverable. Is Read-Write conflict possible in a strict recoverable schedule ?

asked Jan 24 in Databases by anurags228 (23 points) | 8 views

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#made-easy #databases
1) 2) 3) 4) ANS GIVEN IS 1 WHY 3 NOT POSSIBLE?

asked Jan 23 in Databases by 404 found (37 points) | 16 views

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Cascade Rollback and Not recoverable at the same time

asked Jan 18 in Databases by reboot (5 points) | 9 views

+1 vote

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DATABASE GFG QUESTION
Consider the following relations A, B, C. How many tuples does the result of the following relational algebra expression contain? Assume that the schema of A U B is the same as that of A. Table A Id Name Age ---------------- 12 Arun 60 15 Shreya 24 99 Rohit 11 ... Rohit 11 Table C Id Phone Area ----------------- 10 2200 02 99 2100 01 How many tuples will be returned by ?

asked Jan 17 in Databases by donniedarko (29 points) | 25 views

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ACE Chapter 3 Normalization
Consider a relation R(ABCDE) with the following functional dependencies sets. Which of the following below alternative can be decomposed into BCNF without violating dependency preserving? { ABC → DE, DE→ C} { AB→ C , ABD → E , E->D } {ABC->DE , D→ B , E→ C } {ABC → DE , D → EA , A → D}

asked Jan 17 in Databases by Surya_Dev Chaturvedi (5 points) | 16 views

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GATE 2001 DBMS
Suppose the adjacency relation of vertices in a graph is represented in a table Adj(X,Y). Which of the following queries cannot be expressed by a relational algebra expression of constant length? A List of all vertices adjacent to a given vertex B ... of less than three vertices D List all vertices reachable from a given vertex *Please elaborate all the solutions of this question.

asked Jan 15 in Databases by donniedarko (29 points) | 16 views

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Made Easy Test Series, DBMS, Normalization
Can anyone please explain how B) and D) are true? 2NF requires us to have no partial dependency on key for some non-key attributes. 3NF requires us to have no transitive dependency OR X->Y non trivial dependencies where either X is SK or Y are all prime attributes. Can anyone please explain how this leads to options B and D being true? Thanks.

asked Jan 15 in Databases by sankalpmittal (41 points) | 10 views

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1 answer

Made Easy Test Series, DBMS, Functional Dependencies

asked Jan 15 in Databases by sankalpmittal (41 points) | 37 views

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Elmsari Fundamentals , Normalisation
Consider the universal relation A = {P,Q,R,S,T,U,V,W,X,Y,Z} and the set of functional dependencies FD's = { PQ -> R, R -> ST, Q -> U, U -> VW, S-> XY }. What is the key for A. Decompose A into 2NF and 3 NF relations

asked Jan 11 in Databases by Lucifer2440 (5 points) | 11 views

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1 answer

FULL OUTER JOIN
Can anyone please explain how minimum number of tuples in case of Full Outer Join is max(m,n) using a proper example?

asked Jan 8 in Databases by anshumansinha18 (5 points) | 12 views

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The database system then writes out enough information to disk

asked Jan 7 in Databases by Tara22 (13 points) | 12 views

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Gate applied course
If an E-R model says E having at least one multi-valued attribute is converted into relational model say R then what will be the number of simple candidate key possible in R if E has only single attribute as candidate key? A) 0 B) exactly 1 c) more than 1 d) can’t say

asked Jan 6 in Databases by Gopichandankem (5 points) | 27 views

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why we cannot undo a committed transaction
We have the log file that has all information to undo this committed transaction, so why it says we cannot? once a transaction has committed we cannot undo its effect by aborting it.

asked Jan 6 in Databases by Tara22 (13 points) | 20 views

+1 vote

1 answer

NPTEL Assignment Question
S1 : r1(x),r2(x),w2(x),r3(x),w1(x), w2(y),r3(y),w3(x) S2 : r2(x),r1(x),w1(x),w2(x),w2(y),r3(x),w3(x),r3(y) The answer Says Both of them are view equivalent. My Doubt is that there Initial Read Don't ... first and In S2 T2 is reding it first. Same doubt as in this question https://csedoubts.gateoverflow.in/6351/nptel-view-serialisability but it is unclear even in this.

asked Jan 4 in Databases by Sahil91 (683 points) | 29 views

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1 answer

Applied test Series DBMS
Consider the following relation R with attributes as A, B, C, D, and E with functional dependencies (FDs) as marked below: For example, the arrow coming from attribute B is towards the attribute C, therefore, the FD will be B -> C. Which of the ... -prime attributes. Therefore, the relation R is neither in 2NF nor in 3NF. Hence, the correct options are (iii), and (iv).

asked Jan 4 in Databases by Nitinkumar.097 (13 points) | 40 views

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1 answer

THE GATE ACADEMY ts
Does B+ tree support random access?

asked Jan 3 in Databases by Abhineet Singh (23 points) | 33 views

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Self doubt - 2 Phase Locking
Does 2 Phase Locking Protocol ensures a Schedule as recoverable?

asked Dec 30, 2020 in Databases by mani312 (5 points) | 9 views

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1 answer

Made Easy Test series Database Q1
Assume S is a schedule that has both read and write operations with different transactions and different data variables. Also assume all the operations are atomic in nature. Which of the following are true? S with no dirty read then S is ... . S with no dirty read then S is conflict serializable schedule S with no dirty read then S is strict serializable.

asked Dec 29, 2020 in Databases by Shivateja MST (45 points) | 38 views

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restore/recover
What's the difference between recover' and restore'? can we use recover' instead of restore' here? If the transaction does not complete its execution, the database system restores the old values from the log to make it appear as though the ... specifically, it is handled by a component of the database called the recovery system, which we describe in detail in Chapter 19.

asked Dec 28, 2020 in Databases by Tara22 (13 points) | 21 views

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GATE 2017 SET 1 Question 42
What is “Timestamp wrap around” in Timestamp Ordering Concurrency Control?

asked Dec 28, 2020 in Databases by Praddyumn (5 points) | 12 views

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consistence constraints
The text below is from Silberschatz book. Can you please explain how consistence constraints can be verified by integrity constraints? Ensuring consistency for an individual transaction is the responsibility of the application programmer who codes the transaction. This task may be facilitated by automatic testing of integrity constraints, as we discussed in Section 4.4.

asked Dec 26, 2020 in Databases by Tara22 (13 points) | 7 views

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with embedded database accesses in JDBC or ODBC
Is with embedded database accesses in JDBC or ODBC' for the underlined part only or for strikethrough part too? A transaction is a unit of program execution that accesses and possibly updates various data items. ... consists of all operations executed between the begin transaction and end transaction. Introduction to Database Systems, Silberschatz

asked Dec 25, 2020 in Databases by Tara22 (13 points) | 9 views

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1 answer

Made Easy Test Series | Maximum Number of CKs possible simultaneously.

asked Dec 25, 2020 in Databases by Animesh Sinha (25 points) | 132 views

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the computer itself stopped operating
Aren't these two bold parts one thing? I meant when operating system crash the computer stop operating or when computer stop operating definitely operating system stops too why they bring that as two separates aspects? transaction begins to execute but ... (e.g., if it divided by zero), the operating system crashed, or the computer itself stopped operating.

asked Dec 25, 2020 in Databases by Tara22 (13 points) | 27 views

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Databases: recoverability
Assume $S$ is a schedule that has both read and write oeration with different transaction with different data variable. Also assume all the operations are atomic in nature. Which of the following is true? $S$ with no dirty read then $S$ is cascadeless ... own set of data variables. If so then there is no lost update, no cascading rollback and so it is strict recoverable.

asked Dec 24, 2020 in Databases by ytheuyr (2 points) | 5 views

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#databases #made-easy
2PL guarantees serializability ,but it does not prevent deadlocks.2pl has two phases growing and shrinking phase.which of the following rules are used to govern 2pl protocol? two transactions can not have conflicting locks. No unlock can precede a lock operation in ... until all locks are obtained all of these ans given is d .can someone explains why a and c are true?

asked Dec 23, 2020 in Databases by 404 found (37 points) | 6 views

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Made easy Subject Wise Test
Consider the following schedule S with data item x The number of serial schedules which are view equal schedule(S) but not conflict equal to schedule(S) are ________.

asked Dec 16, 2020 in Databases by anurags228 (23 points) | 13 views

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#self-doubt #databases
i found somewhere that lost update problem and ww conflict are different things. Can we say the same regarding that WR conflict and dirty read problem are different? RW conflict and unrepeatable read are different ? please explain if someone knows this?

asked Dec 13, 2020 in Databases by 404 found (37 points) | 14 views

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#made-easy #databases
Consider a disk with block size 512 Bytes. A block pointer 6 bytes and record pointer is 9 bytes. The file has 10000 Employee records. Every record is a fixed length of 120 Bytes. Its key is SSN which is of 4 Bytes. The file is not ordered by the key field and want to ... Index. 1)8 2)7 3) 6 4)4 so here ans given is 7 but i am getting 6 .can someone explains how 7 is possible?

asked Dec 10, 2020 in Databases by 404 found (37 points) | 13 views

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#made-easy #databases
1.Prime attributes of R = {A, B, C, D} 2. ABD is a candidate key of R 3. The relation R is in 1NF but not in 2NF 4.The relation R is in BCNF ans in 1,2,3 but according to me it should be 1,2 bcz CD->E is transitive dependency not functional dependency

asked Dec 10, 2020 in Databases by 404 found (37 points) | 30 views

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#made-easy #dbms
Use the following tables for the below queries wherever table 1 and table 2 are used: A)0 B)1 C)2 D)3 ans is 3.can someone explains how?

asked Dec 10, 2020 in Databases by 404 found (37 points) | 15 views

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GATE2004-IT-73
https://gateoverflow.in/3717/gate2004-it-73 In this question, for one to many relationship with both sides having optional participation, they are taking 3 relations (2 + 1 for multivalued attribute) but if you go by approach given in this ... /database/htmls/chp06.html#mandatory-and-optional-relationships 4 relations will be required. what is the correct approach? i'm confused.

asked Dec 9, 2020 in Databases by Pankaj Dhote (5 points) | 5 views

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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 Dec 3, 2020 in Databases by badman (9 points) | 24 views

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