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Relational
==========
Relational an educational tool to provide a workspace for experimenting with *relational* *algebra*, an offshoot of first-order logic.
It works on GNU/Linux, Windows and OS X.
![screenshot](https://ltworf.github.io/relational/screenshots/3.png)
I test it on GNU/Linux and Windows. It probably works on other systems too.
It provides:
* A GUI that can be used for executing relational queries
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Official website
================
More documentation can be found here http://ltworf.github.io/relational/
More documentation can be found here https://ltworf.github.io/relational/
Install
=======
Binary download for Windows can be obtained from the website.
For Linux, check your distribution's packages, relational is available on Debian and Ubuntu.
Syntax
======
These are some valid queries
```
σage > 25 and rank == weight(A)
σ (name.upper().startswith('J') and age>21 )(people)
Q ⋈ π a,b(A) ⋈ B
ρid➡i,name➡n(A) - π a,b(π a,b(A)) ∩ σage > 25 or rank = weight(A)
π a,b(π a,b(A))
ρ id➡i,name➡n(π a,b(A))
A ⋈ B
```
* Windows: https://ltworf.github.io/relational/download.html?exe
* Debian based: `apt-get install relational`
* Everyone else: Download the sources https://ltworf.github.io/relational/download.html?tar.gz
Run from sources
================
If it needs some dependencies:
* Qt5
* Python 3.4 or greater
* PyQt5
* pyuic5 and pyrcc5
For the dependencies, check `debian/control` for the build dependencies.
You will need to run
```
@ -56,3 +43,26 @@ To launch the application, run
```
./relational.py
```
Syntax
======
These are some valid queries (using the provided example dataset)
```
# Join people and skills
people ⋈ skills
# Select people within a certain age range
σ age > 25 and age < 50 (people)
# Selection with complicated expression requires an extra set of () around the expression
σ (name.upper().startswith('J') and age > 21) (people)
# Cartesian product of people with itself, including only name and id
ρ id➡i, name➡n (people) * π name, id (people)
```
For the selection, python expressions are used.
The syntax is explained here: https://ltworf.github.io/relational/allowed_expressions.html