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0answers
10 views

How to obtain information from foreign keys using ORM in Android? [migrated]

I'm currently using ORM in Android development. However, I seem to be pulling my hair out trying to extract information from foreign keys in the database. I have three separate tables: Player, Game, ...
-1
votes
0answers
8 views

Service TPS optimisation [closed]

I have a service which is backed by Oracle DB & is accessed via a ORM (hibernate). The service is extremely slow i.e. sub 1-TPS (or QPS). How should I go about diagnosing this problem? In the ...
1
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1answer
30 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
27 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
53 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
56 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: ...
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0answers
23 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
157 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
359 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
42 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
27 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
69 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
77 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 ...
0
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0answers
30 views

Boyce-Codd Normal form and violation issue

I have the standard problem of BCNF in front of me, in the table hospital we have: ...
1
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0answers
37 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
17 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
193 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
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0answers
25 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
159 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
36 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 ...
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votes
1answer
154 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
35 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
91 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 $N$ ...
5
votes
2answers
670 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
235 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
116 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
201 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
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2answers
749 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
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1answer
269 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
74 views

relational algebra and SQL

Using the following relations: ...
4
votes
1answer
92 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
54 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
418 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
50 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, ...
2
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1answer
50 views

Optimization of Hierarchical Data Propagation

I have a system in existence which works on parent-child model. They share common attributes, as they belong to same class. A parent can enforces certain data on any user selected attribute, and the ...
0
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1answer
102 views

Static access pattern in Distributed Databases

The access patterns of user requests may be static, so that they do not change over time, or dynamic. It is obviously considerably easier to plan for and manage the static environments than ...
3
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2answers
523 views

What are the different types of databases?

Is there is a study or classification available on different types of databases? (Examples include structured, unstructured, semi structured relational, object oriented, folksonomies, etc.)
-1
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2answers
130 views

How to determine the Utilization and Efficiency of a file server?

I have shown my work below for the problem and would appreciate if someone can let me know if I'm on the right track or point me in the right direction if not. An 8 processor file server handles a ...
5
votes
1answer
67 views

Anonymization of dataset preserving unique identities

The $k$-anonymization paradigm (and its refinements) means to create datasets where every tuple is identical with $k-1$ others. However I'm in a situation where people are in the dataset many times. ...
6
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2answers
91 views

Optimizing a join where each table has a selection

Consider the following query: ...
4
votes
1answer
249 views

How to determine if a database schema violates one of the less known normal forms?

In database normalization, 1NF (no multivalued attributes), 2NF (all non-PK attributes depending only on PK attributes) and 3NF (all non-PK attributes depending on all of the PK attributes) are widely ...