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Relational
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==========
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Relational an educational tool to provide a workspace for experimenting with *relational* *algebra*, an offshoot of first-order logic.
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I test it on GNU/Linux and Windows. It probably works on other systems too.
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It provides:
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* A GUI that can be used for executing relational queries
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* A standalone Python module that can be used for executing relational queries, parsing relational expressions and optimizing them
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* A command line interface
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Official website
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================
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More documentation can be found here https://ltworf.github.io/relational/
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Install
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=======
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* Windows: https://ltworf.github.io/relational/download.html?exe
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* Debian based: `apt-get install relational`
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* Everyone else: Download the sources https://ltworf.github.io/relational/download.html?tar.gz
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Run from sources
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================
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For the dependencies, check `debian/control` for the build dependencies.
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You will need to run
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```
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make
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```
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to generate some .py files.
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To launch the application, run
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```
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./relational.py
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```
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Syntax
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======
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These are some valid queries (using the provided example dataset)
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```
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# Join people and skills
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people ⋈ skills
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# Select people within a certain age range
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σ age > 25 and age < 50 (people)
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# Selection with complicated expression requires an extra set of () around the expression
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σ (name.upper().startswith('J') and age > 21) (people)
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# Cartesian product of people with itself, including only name and id
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ρ id➡i, name➡n (people) * π name, id (people)
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```
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For the selection, python expressions are used.
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The syntax is explained here: https://ltworf.github.io/relational/allowed_expressions.html
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