'esqueleto' is a bare bones, type-safe EDSL for SQL queries that works with
unmodified 'persistent' SQL backends. Its language closely resembles SQL, so
you don't have to learn new concepts, just new syntax, and it's fairly easy to
predict the generated SQL and optimize it for your backend. Most kinds of
errors committed when writing SQL are caught as compile-time errors---although
it is possible to write type-checked 'esqueleto' queries that fail at runtime.
'persistent' is a library for type-safe data serialization. It has many kinds
of backends, such as SQL backends ('persistent-mysql', 'persistent-postgresql',
'persistent-sqlite') and NoSQL backends ('persistent-mongoDB'). While
'persistent' is a nice library for storing and retrieving records, including
with filters, it does not try to support some of the features that are specific
to SQL backends. In particular, 'esqueleto' is the recommended library for
type-safe 'JOIN's on 'persistent' SQL backends. (The alternative is using raw
SQL, but that's error prone and does not offer any composability.)
Currently, 'SELECT's, 'UPDATE's, 'INSERT's and 'DELETE's are supported.
Not all SQL features are available, but most of them can be easily added
(especially functions), so please open an issue or send a pull request if you
need anything that is not covered by 'esqueleto' on
The name of this library means "skeleton" in Portuguese and contains all three
SQL letters in the correct order =). It was inspired by Scala's Squeryl but
created from scratch.