The databases tag has no wiki summary.
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“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 ...
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1answer
71 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 ...
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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 ...
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1answer
29 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 ...
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2answers
75 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 ...
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1answer
25 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 ...
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46 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, ...
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21 views
Optimizantion 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 ...
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62 views
Bond energy and vertical partitioning to get a vertical fragmentation in distributed dbms
Can anybody please solve the following problem step-by-step with explanations, using bond energy and vertical partitioning to obtain a vertical fragmentation of the set of attributes.
I need to ...
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24 views
adjustment and tuning in database [closed]
"It is well known that design and development activity of any kind is an ongoing
process requiring constant monitoring and periodic adjustment and tuning."
What is adjustment and tuning in database ...
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34 views
In DDBMS, What meaning of corresponding sites?
The last step in the design process is the physical design, which maps the local conceptual schemas to the physical storage devices available at the corresponding sites.
What meaning of corresponding ...
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52 views
Top-Down Design Process in Distributed Databases
"There is a relationship between the conceptual design and the view design. In one
sense, the conceptual design can be interpreted as being an integration of user views.
Even though this view ...
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1answer
57 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 ...
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2answers
214 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.)
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83 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 ...
4
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1answer
53 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. ...
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79 views
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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 ...
