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Beam is a highly-general library for accessing any kind of database with Haskell. It supports several backends. beam-postgres and beam-sqlite are included in the main beam repository. Others are hosted and maintained independently, such as beam-mysql and beam-firebird. The documentation here shows examples in all known backends.

Beam is highly extensible and other backends can be shipped independently without requiring any changes in the core libraries.For information on creating additional SQL backends, see the manual section for more.

Beam features

  • Easy schema generation from existing databases
  • A basic migration infrastructure for working with multiple versions of your database schema.
  • Support for most SQL92, SQL99, and SQL2003 features across backends that support them, including aggregations, subqueries, and window functions.
  • A straightforward Haskell-friendly query syntax. You can use Beam's Q monad much like you would interact with the [] monad.
  • No Template Haskell Beam uses the GHC Haskell type system and nothing else. The types have been designed to be easily-inferrable by the compiler, and appropriate functions to refine types have been provided for the where the compiler may need more help.

How to install

Beam is available via Hackage and Stackage, and can be included in your stack project by adding beam-core and an appropriate beam backend to your stack.yaml as an extra-dep. Some projects may want to follow the latest master, for the newest features. If so, put the following in your stack.yaml to build and use beam in your project!

packages:
- .
- location:
    git: https://github.com/tathougies/beam.git
    commit: a3b5e0763843fed48c7eef53fa7d08cfe710342d
  extra-dep: true
  subdirs:
    - beam-core
    - <backend>

Note

the commit will need to be changed to whatever the latest commit of master is, or whichever commit you want to build from even.

and add the following to your .cabal file, in the build-depends section:

beam-core,
<backend>

You may alse want to add the beam-migrate package if you want to manage your database schemas in Haskell as well.

Available backends are:

  • beam-postgres -- A feature-complete backend for the Postgres RDBMS. See the beam-postgres documentation for more information.

  • beam-sqlite -- A feature-complete backend for the Sqlite library. Note that SQLite does not support all SQL92 features, so some of the examples may not work. Refer to the beam-sqlite documentation for more information on compatibility.

  • beam-mysql -- A backend for MySQL or MariaDB. Maintained separately on GitHub.

Quick Start Guide

For those looking to get started with beam, we first recommend you go through the tutorial. The user guide contains much more detailed reference-like information. Finally, the documentation on hackage is always available (although the types may seem obtuse).

If you're interested if beam supports your favorite database feature, refer to the documentation for your backend or take a look at the compatibility matrix.

How to Contribute

We always welcome contributions, especially to cover more database features or to add support for a new backend. Help is available on the beam-discussion Google Group. The following is a quick step-by-step guide of contributing a new feature:

  1. Fork the github repository at https://github.com/tathougies/beam and clone the fork to a local directory.
  2. Work on your feature on your own branch, or pick an issue.
  3. When you feel ready to contribute the feature back to beam-core, send a Pull Request on Github, with an explanation of what your patch does and whether it breaks the API.
  4. Respond to community comments and rework your patch.
  5. When the maintainer feels comfortable with your patch, he will commit it to the master branch and it will be included in the next minor version. API-breaking changes will not be included until the next major version.

Tip

Be sure to add your name to the CONTRIBUTORS file for eternal fame and glory!

Questions, Feedback, Discussion

  • For frequently asked questions, see the FAQ.
  • For general questions, feedback on patches, support, or other concerns, please write to the mailing list
  • For bugs or feature requests, please open an issue

Why Beam?

Beam is the most feature-complete, turnkey Haskell database solution out there. It supports the bulk of the SQL92, SQL99, SQL2003, SQL2006, SQL2008, SQL2011, and SQL2016 specifications, as well as the entire breadth of features of each of its backends. See the compatibility matrix. You will rarely be forced to write a SQL query 'by hand' when using Beam (but you can).

Additionally, Beam plays nice with the rest of the Haskell ecosystem, the standard Beam backends are all implemented in terms of pre-existing Haskell packages. Beam does not intend to make every query work across every database, and you are free to write queries in beam's DSL that only work on particular backends, using type classes to restrict which backends work. It is assumed that you have chosen you RDBMS with much care, and we want to support you in that. Beam's main purpose is to marshal data back and forth, to serve as the source of truth for the DB schema, and to generate properly formed SQL from Haskell expressions.