Questions tagged [relational-dbms]

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Pushing down Group By clause [closed]

I've studied this exercise in class But I cannot figure out why, when I push down the Group By clause, I can remove RLCode attribute from GroupBy. Does this action change the meaning of query tree?
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10 views

Inserting performance on a Graph Database

In the book "Nosql Distilled" by Fowler, in the section about the comparison between relational model and graph model, it's said that the problem with graph databases is the poor performance on ...
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18 views

Relational Model Vs Aggregate-oriented Model

Can you explain to me why the relational model is not good to deal with aggregates? At the contrary, in which cases we can prefer a relational model to an aggregate-oriented model ? Thanks
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11 views

DBMS - Indexed Sequential Files

If i already have a primary index on a file, what is the purpose of ordering also the records of the file by primary key ? Can't i simply use the primary index to get a fast access to records without ...
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9 views

DBMS - Heap file organization for Secondary Indices

In my book about Database Management Systems the authors say that the Heap file organization (the records are put in the disk blocks following the inserting order) is usually associated with secondary ...
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8 views

Utility of using a Primary Index in a relational dbms

If the records stored in each block are ordered by the primary key, what is the vantage of using a primary index? In fact, without a primary index, I still can do a binary search: taking the block in ...
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21 views

Minimal Fragmentation in Distributed Database

In a distributed database, using selection we get a minimal fragmentation if If all the predicates of a set Pr are relevant, Pr is minimal. Given fragments generated by a set $M(P)$, we say a ...
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1answer
27 views

Do DBMS decrease Memory requirements?

I finished my Economics thesis using RStudio, but my script was very slow due to massive RAM consumption during the process. My Case I had a massive dataset (stock prices in daily frequency for 10 ...
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1answer
4k views

Storing Big Matrix in DataBase

I have a mysql database with the following format: id string 1 foo1... 2 foo2... .. ... There are >100k entries in this db. What I want ...
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1answer
302 views

Relational Data Mining without ILP

I have a huge dataset from a relational database which I need to create a classification model for. Normally for this situation I would use Inductive Logic Programming (ILP), but due to special ...
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5answers
365 views

The data in our relational DBMS is getting big, is it the time to move to NoSQL?

We created a social network application for eLearning purposes. It's an experimental project that we are researching on in our lab. It has been used in some case studies for a while and the data in ...