# Recent questions tagged databases

0 votes
0 answers 31 views
Can anyone suggest me any good resource or videos for self studying gate CSE maths and Database.I need to finish them fast... DATABASE MANAGEMENT SYSTEMS Syllabus ER-model. Relational model: relational algebra **, tuple calculus **, SQL. Integrity constraints ... .in/281290/how-do-i-prepare-engineering-mathematics-for-gate-cs https://drive.google.com/file/d/0Byt7-j-JD0d0bmxlRkZGcjN2cjA/view
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1 answer 15 views
Consider the following schedule S: S: R1(X); R2(Z); R1(Z); R3(X); R3(Y); W1(X); W3(Y); R2(Y); W2(Z); W2(Y); Here Ri(D) denotes that transaction i is reading the data item D while Wi(D) denotes that transaction i is writing the ... operation of the transaction can be added in the end of schedule S in an appropriate order such that S is recoverable. The number of such orders possible are ______
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1 answer 17 views
T1 T2 T3 R(A) R(A) W(A) W(A) My approach: Initial reads by: T1 and T2 Final write by: T1 No, Write Read So, T1->T3, T2->T3, and T2->T1 and since T1 occurs last therefore, (T3, T2) → T1 Therefore, T1->T3->T1 and T3<-T2->T1
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1 answer 18 views
Consider the relation R(ABCDEF) with dependecies F: {A->C, C->D, B->E, E->F} The number of tables present in its 2NF decomposition are _______.
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1 answer 187 views
I am making a list of different types of numericals that can possibly come in GATE from different subjects .. This list is not comprehensive, so please ... ?fbclid=IwAR0ezzTYvJdobF2hXtr3xVNZpZOFtw96yHAywR2_j9BOKGe1mBNSgVUcsvw#9xiori58gq22i 7. https://www.mediafire.com/folder/gp6z7khjzyl8d/gate_materials?fbclid=IwAR0ezzTYvJdobF2hXtr3xVNZpZOFtw96yHAywR2_j9BOKGe1mBNSgVUcsvw#mp3qyi2prh3fb
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1 answer 50 views
3 Tables , person( Aadhar No. , P .Name, P. addres) Feculty( Aadhar , Salary) Student( Adhar , S_fee,year) can be make 2 table like below in total specialization? Feculty( Aadhar , P .Name, P. addres, Salary) Student( Adhar, P .Name, P. addres , S_fee,year) because I got question in 1 test series where they are saying total specializtion concept wrong.Please show , 2 Tble made are coorect?
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0 answers 13 views
hi i am confused with these 3 books as i read GO or any web so all they recommend these 3 and say use these 2 specially (navathe and korth). so i want to ask a question is what one specific book i use to study for all syllabus for dbms or particular ... to topic of syllabus what should i read? which particular topic is good in which book please solve my query cause i stuck in between thank you
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0 answers 6 views
For the following information systems determine the entities of interest, their attributes and the relationships that exist between the entities. Draw the E-R diagram for the system. Peoples Information Systems for a village/ward(that stores information about peoples)
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1 answer 16 views
Consider the following (incomplete) schedule S: T1:R(X), T1:R(Y), T1:W(X), T2:R(Y), T3:W(Y), T1:W(X), T2:R(Y) If all three transactions eventually commit, show the serializability graph.
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0 answers 9 views
Consider the following (incomplete) schedule S: T1:R(X), T1:R(Y), T1:W(X), T2:R(Y), T3:W(Y), T1:W(X), T2:R(Y) If all three transactions eventually commit, show the serializability graph.
1 vote
1 answer 22 views
It is 2NF or not ? Just explain this portion.
0 votes
0 answers 11 views
Lets suppose, we define a schema with no primary key but there is an attribute(s) with unique and not null constraints. Now default indexing i.e primary indexing is not possible here because of no primary key. Now, at the time of Database design, If i write ... is it necessary to input records in sorted order? or is there any other way possible to apply clustering index over a given database file?
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0 answers 8 views
Consider the following relations concerning a driving school. The primary key of each relation is in boldface. STUDENT(S_Name,Class_No,Th_Mark,Dr_Mark) S_Name - student name, Th-Mark - Theory mark, Dr_Mark - driving mark STUDENT_DRIVING_TEACHER(S_Name,Dr_T_Name) Dr_T_Name - driving ... more marks than average theory mark of class 8. f)Find the list of teachers who can drive all the vehicles.
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0 answers 8 views
Is the JOIN operations(natural , left , right) in relational algebra and SQL same or is there any difference based on the condition? Please provide reference.
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0 answers 7 views
How to find the number of relations required for a self-referential relationship with all the cardinalities mapped with total and partial participation? Please provide links to the same.
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0 answers 20 views
R(A,B,C,D) is a relation. FD given is:{ AB->C , C->AD } is it in 2NF? is it in 3NF?
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1 answer 21 views
When switching the CPU between two processes.. which of the following applies A. The PCB is both, saved and reloaded, only for the interrupted process that is existing the CPU B. The PCB is saved for the process that is scheduled for the CPU C. The PCB is reloaded for the process that is scheduled for the CPU D. No PCB is saved or reloaded E. None of the above
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0 answers 24 views
So recently I have been studying minimization of ER diagrams and have come across a big confusion. So if 2 entities, E1 and E2 are related to each other with one to one cardinality and E1 has Total participation and E2 has Partial participation, How many minimum tables will ... the answer is 1, but some sources also say that answer should be 2. Also for GATE exam which one should be considered ?
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0 answers 28 views
Why in this question use B-->A ,A-->C ?
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0 answers 8 views
What is right replication policy in database? And how is it different from right biasing?
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1 answer 30 views
is it true that “every strict schedule is cascadeless schedule”?
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0 answers 38 views
Relation R (A,B,C,D) with FD'S { A->B, B->C, C->D, D->A } then relation R is decomposed into two relations R1 and R2 such that it is satisfying second normal form, third normal form and BCNF and decomposition is lossy. Then how the attributes are distributed in these two decomposed relations R1 and R2? Note: U is the set of all attributes. 1. 2. 3. 4.
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0 answers 19 views
Given 3 T1, T2 and T3 transactions which have (2,2), (3,2), (4,2) read and write operations respectively the no of schedules possible using these three transactions are A. 1260 B. 630630 C. 6 D. 63000
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0 answers 93 views
Given the following relations and SQL query: Student (sid, name, age, address, date of birth, level) Book(bid, title, author) Checkout(sid, bid, date_borrowed, date_returned) SELECT S.sid, S.level, C.date_borrowed, C.date_returned FROM Student S, Book B, Checkout C ... correctness of the query using a Relation Connection Graph.[5 marks] d) Represent the query above using a query tree. [5 marks]
1 vote
2 answers 72 views
Suppose we have two entity sets person, Email and use a relationship Owns. A person own atmost one email account but an email account can be owned by multiple persons. Which of the following is an ER diagram based on above description.
1 vote
1 answer 34 views
What is degree of Self Referential Relationship? Unary or Binary?
3 votes
3 answers 62 views
Q. R(A,B,C,D,E,F) with {A,BC,CD} candidate keys.How many super keys possible?
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0 answers 18 views
Can Somebody know how to design ER Diagram from this ?
4 votes
4 answers 956 views
Consider the following statements $S1$ and $S2$ about the relational data model: $S1$: A relation scheme can have at most one foreign key. $S2$: A foreign key in a relation scheme $R$ cannot be used to refer to tuples of $R.$ Which one of the following choices is correct? Both $S1$ and $S2$ are true $S1$ is true and $S2$ is false $S1$ is false and $S2$ is true Both $S1$ and $S2$ are false
1 vote
2 answers 556 views
The relation scheme given below is used to store information about the employees of a company, where $\textsf{empId}$ is the key and $\textsf{deptId}$ indicates the department to which the employee is assigned. Each employee is assigned to exactly ... than the average salary of employees in the department employees in the company female employees in the department female employees in the company
0 votes
2 answers 706 views
Let $S$ be the following schedule of operations of three transactions $T_1$, $T_2$ and $T_3$ in a relational database system: $R_2(Y), R_1(X), R_3(Z), R_1(Y)W_1(X), R_2(Z), W_2(Y), R_3(X), W_3(Z)$ Consider the statements $P$ and $Q$ below: $P$: $S$ is conflict- ... correct? Both $P$ and $Q$ are true $P$ is true and $Q$ is false $P$ is false and $Q$ is true Both $P$ and $Q$ are false
0 votes
1 answer 611 views
Suppose the following functional dependencies hold on a relation $U$ with attributes $P,Q,R,S$, and $T$: $P \rightarrow QR$ $RS \rightarrow T$ Which of the following functional dependencies can be inferred from the above functional dependencies? $PS \rightarrow T$ $R \rightarrow T$ $P \rightarrow R$ $PS \rightarrow Q$
5 votes
2 answers 1K views
Suppose a database system crashes again while recovering from a previous crash. Assume checkpointing is not done by the database either during the transactions or during recovery. Which of the following statements is/are correct? The same undo and redo list ... any further All the transactions that are already undone and redone will not be recovered again The database will become inconsistent
3 votes
1 answer 1.7K views
A relation $r(A, B)$ in a relational database has $1200$ tuples. The attribute $A$ has integer values ranging from $6$ to $20$, and the attribute $B$ has integer values ranging from $1$ to $20$. Assume that the attributes $A$ and $B$ are independently distributed. The estimated number of tuples in the output of $\sigma _{(A>10)\vee(B=18)}(r)$ is ____________.
0 votes
1 answer 513 views
The following relation records the age of $500$ employees of a company, where $empNo$ (indicating the employee number) is the key: $empAge(\underline{empNo},age)$ ... one other employee Employee numbers of all employees whose age is not the minimum Employee numbers of all employees whose age is the minimum
3 votes
3 answers 480 views
Let $r_i(z)$ and $w_i(z)$ denote read and write operations respectively on a data item $z$ by a transaction $T_i$. Consider the following two schedules. $S_1: r_1(x)r_1(y)r_2(x)r_2(y)w_2(y)w_1(x)$ ... $S_2$ is conflict serializable Both $S_1$ and $S_2$ are conflict serializable Niether $S_1$ nor $S_2$ is conflict serializable
1 vote
5 answers 928 views
Consider the relation $R(P,Q,S,T,X,Y,Z,W)$ with the following functional dependencies. $PQ\rightarrow X;\quad P\rightarrow YX;\quad Q\rightarrow Y; \quad Y\rightarrow ZW$ Consider the decomposition of the relation $R$ into the constituent relations according to ... , but $D_2$ is a lossless decomposition Both $D_1$ and $D_2$ are lossless decompositions Both $D_1$ and $D_2$ are lossy decompositions
1 vote
0 answers 29 views
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 records. Also ... that each record fits into one disk block. The minimum number of disk accesses required to retrieve any record in the database is ______.
0 votes
0 answers 29 views
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.
0 votes
0 answers 44 views
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 ___________.