Really Simple (and quite inefficient) Relational Algebra parser and SQL converter

Very simple Relational Algebra to SQL converter. Designed for educational purposes only.

The tool also provides a simple Relational Algebra to LaTeX mathematical expression.

Usage

ra-to-sql can be installed as a Node.js package or as a JavaScript library (see Installation section for more detailed information). The ra-to-sql.js library can be downloaded from here, or used from a CDN https://unpkg.com/ra-to-sql.

As a JavaScript library:

var sql = raToSql.getSQL(<<ra-expression>>);
var latex = raToSql.getLatexExpression(<<ra-expression>>);

As a Node.js app:

var raToSql = require('ra-to-sql');
var sql = raToSql.getSQL(<<ra-expression>>);
var latex = raToSql.getLatexExpression(<<ra-expression>>);

Where <<ra-expression>> is any valid Relational Algebra expression.

Currently, the following operations are supported

• Rename: Ren[a,b](A), ρ[a,b](A)
• Projection: Proj[a,b](A), π[a,b](A)
• Selection: Sel[Condition](A), σ[Condition](A)
• Cartesian product: A x B, A × B
• Natural Join A |x| B, A ⋈ B
• Theta Join A |x(Condition)| B
• Union: A U B, A ∪ B
• Intersection: A INT B, A ∩ B
• Set Difference: A - B
• Asignment: A <- B
• Asignment with Rename: A(a,b) <- B

The structure of the language is quite simple, here are a few rules:

• Operations can be nested
• There are two types of sentences:
  • Assignments
  • Result (any sentence without an assignment)
• Parser ends evaluating when a "Result" sentence is found. If no Result sentence is found, the last assignment is considered the Result sentence
• Semicolon (;) and New Line are both valid as sentence separator

The following are examples of valid set of sentences:

A(a,b) <- Proj[PersonId,PersonName](Person)
A x A x A

OldPeople <- Sel(Age>80)(Person); Person |X| City;

Sel[Number > 14 AND !(Number = 15 OR Number = 18)](Numbers)

You can try it online here:

• SQL.
• LaTeX expression.

Note: The SQL generated is compatible with SQL Server and sqlite.

Installation

CDN

<script src="https://unpkg.com/ra-to-sql@<version>/dist/ra-to-sql.js"></script>

Replace <version> with expected version number. For example https://unpkg.com/[email protected]/dist/ra-to-sql.js

Node.js

npm install ra-to-sql

For contrinutors

Pre-requisites

• Node.js

Setup

Fork/Clone the repository (https://github.com/jrebagliatti/ra-to-sql)

Install the dependencies:

nmp install

Update the code

The following are the main components of the library:

• src/grammar/ra.jison contains the definition of the grammar (tokens and BNF) in Jison format
• src/sql_scope.js contains the transformations for converting to SQL
• src/mathjax_scope.js contains the transformations for converting to LaTeX
• src/ra-to-sql.js is the entry point of the library

Additionally, the following files are generated as part of the building process:

• src/ra.js: Is the RA parser, which is built automatically using the Jison parser generator. Run npm run jison to generate it.
• dist/ra-to-sql.js: Is the JavaScript library, which is bundled using the Webpack bundler. Run npm run build to generate it.

Running the tests

Tests are defined in the test/test-definitions folder. Each Json file included in that folder becomes a test. File structure is self-explanatory.

Use the following command to run the tests:

npm test

Built With

• Jison - Parser generator
• Webpack - Web module bundler
• sqlite3 - Used to test generated SQL
• mocha - Test framework
• csv-parser - CSV Parser

Contributing

Any contribution is welcomed!. There are no guidelines for contributing, just common-sense.

Versioning

We use SemVer for versioning. For the versions available, see the tags on this repository.

Authors

• Javier Rebagliatti (Database Systems teaching assistant at Universidad de La Matanza) - Initial work - jrebagliatti

See also the list of contributors who participated in this project.

License

This project is licensed under the MIT License.