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purescript-selda

About

purescript-selda is an SQL library (eDSL) which allows a user to write type-safe queries.

• Generated SQL is guaranteed to be correct by the type system.
• It supports arbitrarily nested queries with capabilities of filtering, joins and aggregation.
• We used standard monadic abstraction which supports writing queries in a linear, natural style.
• Our main target is PostgreSQL though in the upcoming release (already on master) we add SQLite3 support (with ability to support other db backends).

Example Query

To declare a type for a SQL table (already created in the db) we write the following table definition:

people ∷ Table (id ∷ Int, name ∷ String, age ∷ Maybe Int)
people = Table { name: "people" }

Once we've defined the tables, we can write queries, e.g.

selectFrom people \{ id, name, age } → do
  { balance } ← leftJoin bankAccounts \b → id .== b.personId
  restrict $ id .> lit 1
  pure { id, balance }

Generated SQL for the above query:

SELECT people_0.id AS id, bank_accounts_1.balance AS balance
FROM people people_0
LEFT JOIN bank_accounts bank_accounts_1 ON ((people_0.id = bank_accounts_1.personId))
WHERE ((people_0.id > 1))

For a more gentle introduction and more examples please refer to the Step-by-Step Guide.

More Help

If you have any questions please don't hesitate to ask. <br>I'll be happy to help and provide any guidance if necessary. <br>Open an issue or hit me up directly (either on slack, forum or directly via email).

Install

Install postgresql-client's dependencies

npm install pg decimal.js

Info

• Introductory Guide: End-to-End example: how to setup, write queries, use aggregation, deal with type errors and execute queries and inserts.
• Advanced Guide: Custom Types and Expressions (litPG, Any, EForeign, custom PG functions), more flexible table definitions (Source, db schemas, set-returning functions) - unsafe escape hatches
• Test Suite: For information about features, examples, usage, etc. refer to the test suite: Test.Common, Test.PG, Test.SQLite3. To run the tests, docker-compose up -d helps to prepare postgres database.
• Documentation: Pursuit docs
• My thesis

Credits

Supported by Lambda Terms

Inspired by selda