Introduction

This project was written for a university course about theoretic computer science.

It is written in Python and can evaluate SPC-Queries on a given database. SPC-queries are a subset of relational algebra where only σ (selection), π (projection) and x (cartesian product) are available. The SPC-Version can now be found on an extra branch. The master branch will develop more features.

Usage

You can use make shell to start the database shell or you can just run the spcShell.py file with python3. The following usage is also valid.

python3 spcShell.py <database file>
python3 spcShell.py <database file> query

Commands

open <filename>     opens a database file
tables              lists the loaded tables
<spc-query>         a valid query will automatically be evaluated

Examples

Instead of σ and and π you can use * for selection and # for projection.

# all people and their living countrys
% python spcShell.py example.txt '#1,7(*1=4(*6=5(People x Living x Places)))'
Database loaded
>>Query executed as π1,7(σ1=4(σ6=5(People x Living x Places)))
('Alfred', 'Germany')
('Superman', 'America')
('Jesus', 'Jerusalem')
('TomRiddle01', 'Germany')


# all people from Hamburg
% python spcShell.py example.txt '#1(*5="Hamburg"(*1=4(People x Living)))'
Database loaded
>>Query executed as π1(σ5="Hamburg"(σ1=4(People x Living)))
('Alfred',)
('TomRiddle01',)

Test

To run the unittests use make test.