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0
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1answer
19 views

Database normalization impractical

After third form normalization, extra tables shall be created. And the functional determinant are used as primary key in the new table, as foreign key in the modified old table. My question is that ...
-1
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0answers
16 views

Serialization graph - confusion

I don't know how to produce a serialization graph from the following information. As where I've highlighted every possible Read/Write, Write/Read and Write/Write. They are dealing with different ...
0
votes
1answer
16 views

What is the difference between a prime attribute and a proper subset of the candidate key?

I am taking DBMS classes and am currently studying the various normal forms. The following is the definition of a Prime Attribute I learned in class: ...
0
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0answers
53 views

two phase locking and a contest question?

In 2PL (two phase locking), what advantage(s) does the rigorous model have over the strict model? I) There is no advantage over the strict model. II) In contrast to the strict model, it ...
1
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0answers
36 views

Concurrency Control: Two phase locking

A schedule is given as follows: TI:R(X) T3:R(Y) T2:W(X) T3:W(Y) T3:R(X) T1:R(Y) T2:W(Y) where R(X)=read x and W(X)=write x Is this schedule executable under two-phase locking protocol with upgrade ...
0
votes
1answer
23 views

How can I formalize key value stores with set theory?

I'm currently developing a simple key-value NoSQL store and want to build its formal model. I found article about key value formalisation with category theory, but I'm interested are there some works ...
2
votes
2answers
69 views

Linearizability and Serializability in context of Software Transactional Memory

I've been trying to grasp serializability and linearizability in the context of software transactional memory. However, I think both notions can be applied to transactional memory in general. At this ...
2
votes
0answers
43 views

How to generate globally unique timestamps for transactions in distributed database systems?

According the paper [1] (Section 4), timestamp ordering (T/O) is a technique whereby a serialization order is selected a priori and transaction execution is forced to obey this order. In the ...
0
votes
1answer
26 views

Information Systems (IS) and Data Warehouse

I'm working on a research project about the adoption of DWH systems and doing some literature review I find many documents that refer to Information System. I tried to find the right definition of ...
2
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0answers
61 views

Rollback and Timestamp Ordering in Database

If we use the Timestamp Ordering for concurrency control in following scheduling: My TA says T2,T3,T5 is Run and T4,T5 is Rollback. I think it's false. any expert could help us?
4
votes
1answer
21 views

n closest points in a set of lat/long coordinates

Here's my problem: I have a website where people can search based on their location (which is converted to lat/long coordinates). I have many products stored in a database with their lat/long ...
-1
votes
0answers
48 views

Could there be an end of (human-organized) databases? [closed]

I'm not a computer science guy but just curious about a potential decline of databases. I believe there will always be data, that's for sure, but would there always be databases? Databases are a ...
0
votes
1answer
33 views

Terminology for describing a kind of server [closed]

What is the adjective used to describe the fact that a server keep track of queries made by a user. I take the example of a database server.
0
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0answers
13 views

is it possible to combine 2 relation with an entity set for rdbms minimization?

E1 is a weak entity set. E2 and E3 are other two entity sets. E1 is related to E3 via a weak relation R1 cardinality is many to 1 and E1 is connected to E3 via R2 with cardinality many to 1. Now in ...
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vote
2answers
71 views

When should you use the existential and universal quantifiers for Relational Calculus?

Could someone explain to me WHEN do you use existential and universal quantifiers for Relational Calculus? Given this schema: Hotel(hotelNo, hotelName, city) ...
2
votes
0answers
75 views

What is a best known algorithm for finding diameter of undirected graph?

What is best known algorithm (approximate or exact) for finding diameter of a large undirected graph? The diameter is defined as longest of shortest paths between any two nodes. I know that naive ...
3
votes
1answer
175 views

Can a schedule with cyclic precedence graph still be serialisable?

We know Every conflict serializable schedule is serializable, but not all serializable schedules conflict-serializable. (*) so it means there is at least one serializable schedule that not conflict ...
1
vote
0answers
21 views

1-serializability theorem in database theory

In the paper "MVCC@TODS'1983 by Bernstein et al.", 1-serializability ($1$-$\text{SR}$) problem is defined as a decision problem: To decide whether an MV (multi-version) log $L$ is $1$-$\text{SR}$. ...
1
vote
1answer
48 views

A relationship in a UML class diagram

I am investigating a small database in a paper: Each line is a selling record. For instance, Line 2 expresses that ...
0
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0answers
31 views

Definition of 3NF

We've been studying relational database design in the last semester, and I was missing a lot of lecturers, so I decided to stick to the course's book, Database Systems; The Complete Book, to make up ...
2
votes
1answer
59 views

What actually is the concept of transparency? Why not call it Abstraction?

I searched this over Google few times but ended up with articles on transparency rather than an answer. With relation to distributed database study(or distributed OS), what is the concept of ...
0
votes
1answer
85 views

Automatically generate meaningful queries for a data table

My field of research is not Database or AI. But I have some problems to solve, and would like to know which branch this kind of problems belong to, and what are the results. The main question is: ...
0
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0answers
29 views

1NF to 2NF, do the functional dependencies remain?

When decomposing from 1NF to 2NF, is there a guarantee that the functional dependencies don't change in regards to the original relation? Example: ...
0
votes
2answers
275 views

B-Tree and how it is used in practice

I understand what a B-Tree is (I already implemented a B-Tree in Java with insert and delete methods that preserve the invariant). However I do not understand exactly how it is used for example for ...
3
votes
1answer
1k views

Difference between data duplication and data redundancy

My Computing teachers talk about data duplication and data redundancy in terms of databases as different things, but I'm struggling to differentiate them. The context is database normalisation, and in ...
1
vote
1answer
46 views

Partial Range Query on Inverted File with Combined Index

I am currently reading Multidimensional and Metric Data Structures by Hanan Samet for fun. The combined index is discussed on page 5-6. I do understand it in the sense that the inverted file itself is ...
0
votes
2answers
28 views

Determine Epsilon for identification [closed]

I have a project in which I need to compare different distances in a database with a distance in input in order to identify a person. For that I use this expression: DistanceDB - DistanceInput < ...
2
votes
1answer
74 views

Does “serializable” also mean that it's lockable

Here's an final exam question for a Database Fundamentals class. I've read the book, stuff online.. I can't figure out if "serializable" also means that the schedule is ...
0
votes
1answer
83 views

Functional dependencies with the same key?

let's consider a table with carID | hireDate | manufactory | model | custID | custName | outletNo | outletLoc I want to evaluate all the functional dependencies ...
1
vote
0answers
40 views

Relational calculus: what is a range-restricted variable?

I know that if the set of free variables for a relational calculus query is equal to the set of range-restricted variables then the query is (roughly) safe. I also can identify free variables. ...
1
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0answers
18 views

In search for toy relations to test relational algebra

Does anybody know any toy database / relations that are particularly good and also complete to demonstrate and test relational algebra concepts? I'm hoping some database researchers should have ...
0
votes
5answers
327 views

What is the best way to index lookups on a 2D array of integers that is boundless in x and y?

Lets say you have a data model that consists of a 2D grid of integer points. This grid is sparsely populated and boundless in x and y (up to the max of a 32-bit integer). What is the best way to ...
1
vote
0answers
27 views

How to display distinct rows from single column without using DISTINCT keyword and count() function? [closed]

How to display distinct rows from single column without using DISTINCT keyword and [having count(*) > 1 ] ? My question is can we do this using sub-queries or co-related sub query ? If yes how we can ...
0
votes
1answer
456 views

Resolving many to many relationships?

I'm trying to separate a weird relationship. It goes like this: One waiter can serve more than one kind of drink and one kind of drink can be served by more than one waiter. One waiter can wear more ...
2
votes
0answers
39 views

The research area of data exchange format,i.e. the format that stores serialized objects [closed]

As we know, if we want to design and implement a programming language like JAVA, C++ and C language, we will reference the compilation theory. Similarly, if we would like to design and implement a ...
-2
votes
1answer
238 views

Number of concurrent schedules in database

In a database system, say there are $N$ transactions each having $m_1,m_2,\dots,m_N$ operations. How many concurrent schedules are possible? $(m_1+m_2+....+m_n)!$ is the number of possible ...
0
votes
1answer
36 views

result after applying on delete cascade

In this table B is foreign key referring to the primary key A with on delete cascade option.What will be the result after deleting (4,3) and how A:1 4 2 9 3 5 B:3 3 4 2 9 4
0
votes
1answer
111 views

E-R diagram and relationships

Suppose we have two entities $A$ and $B$ and some relationship between them. If there is an $M:N$ relationship between them (i.e. an $M$ on the line connecting $A$ to the relationship and an $N$ ...
6
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2answers
868 views

Who needs linearizability?

I've been reading about the differences between serializability and linearizability, which are both consistency criteria for replicated systems such as replicated databases. However, I don't know in ...
1
vote
1answer
318 views

Find similar vector by Locality Sensitive Hashing

I have many vectors in my database. They are in high dimensions such as: $v_1$ : $\langle 23, 23, 1, 33, 103, 219, \dots \rangle$ $v_2$ : $\langle 92, 83, 1, 33, 239, 192, \dots \rangle$ ... I ...
1
vote
1answer
122 views

Preventing oversell, allocation of limited resources with overlapping properties

I am trying to solve problem of preventing oversell of limited resources. Consider resources (people) who are described by set of properties where each property belongs to different category (example ...
2
votes
3answers
272 views

What is the difference between Transitive Closure and Join?

In database theory, there is a notion of transitive closure over relations. I am wondering if join operator over relations is also a special case of transitive closure?
1
vote
2answers
1k views

“At least one” clause in Relational Algebra

I'm fairly new to the syntax of relational algebra, and I'm having a hard time understanding how I could set a "at least one" clause. Example: I have: a table with books (listing the title, year ...
1
vote
1answer
331 views

Are all databases reducible to this ultimate abstract database design?

I've designed a few databases in my time, and on more than one occasion the drive to abstract common elements from specific tables has led me to create generic top-level tables which contain those ...
0
votes
1answer
81 views

relational algebra and SQL

Using the following relations: ...
4
votes
1answer
100 views

Computing number of block reads given relational algebra statement

So I'm just starting to learn about query processing and such in databases and I'm having some trouble. I don't really understand how to compute the minimum number of block reads given a relation and ...
1
vote
1answer
60 views

Approximate time for selection operation using index when equality is on nonkey

In database query processing, the approximate time for selection operation using primary index when equality is on key is $2(b_s + b_t)$ where $b_s$ is disk seek time and $b_t$ is disk transfer time ...
2
votes
2answers
577 views

What is semantic closure?

In the context of database theory, what does semantic closure mean (linguistically speaking, i.e. not the mathematical definition) If X is the set of attributes of $F$, then the semantic closure ...
1
vote
1answer
51 views

Random file access in a block based file format

I am writing a program to store, retrieve and delete "blocks" of data of varying sizes. The way it currently works is by keeping a database storing the locations of the blocks and the locations of ...
2
votes
0answers
48 views

Algorithm for query comparison

Lets say I have a global dataset and I run queries over those data set. For example my dataset would be #id, #Name, #Employee, #Birthdate, #number_of_children 1, Nick, Nasa, 1982, 1 2, Jack, Exon, ...