Beam is a Haskell interface to relational databases. Beam uses the Haskell type system to verify that queries are type-safe before sending them to the database server. Queries are written in a straightforward, natural monadic syntax. Combinators are provided for all standard SQL92 features, and a significant subset of SQL99, SQL2003, and SQL2008 features. For your convenience a thorough compatibility matrix is maintained here.
Beam is standards compliant but not naive. We recognize that different database backends provide different guarantees, syntaxes, and advantages. To reflect this, beam maintains a modular design. While the core package provides standard functionality, beam is split up into a variety of backends which provide a means to interface Beam's data query and update DSLs with particular RDBMS backends. Backends can be written and maintained independently of this repository. For example, the beam-mysql and beam-firebird backends are packaged independently.
Recognizing that over-abstraction frequently means caving in to the lowest common denominator, Beam does not do connection or transaction management. Rather, the user is free to perform these functions using the appropriate Haskell interface library for their backend of choice. Additionally, beam backends provide a significant portion of backend-specific functionality which seamlessly fits into the beam ecosystem.
For example, the beam-postgres backend is built off of the postgresql-simple
interface library. When using beam-postgres, the user manages connections and
transactions with postgresql-simple. The user is free to issue queries
directly with postgresql-simple, only using beam when desired. Postgres offers
a number of rich data types on top of the standard SQL data types. To reflect
this, beam-postgres offers pluggable support for postgres-specific data types
and features.
For more information, see the user guide.
For questions, feel free to join
our mailing list or
head over to #haskell-beam on freenode.