test postgres adapter

psql-test.hs

{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE ScopedTypeVariables #-}
import qualified Data.Text as Text

import Database.PostgreSQL.Simple
import Control.Monad
import Control.Applicative
import Data.Maybe

queryStuff :: IO ()
queryStuff = do
  conn <- connectPostgreSQL "dbname='test_db'"

  xs <- query_ conn "select email,encrypted_password from users"
  forM_ xs $ \(email,encrypted_password :: Maybe String) ->
    putStrLn $ email ++ fromMaybe "n/a" encrypted_password

main = do
  queryStuff

Toy program to see how to work with values that are not guaranteed to be present with
Database.PostgreSQL.Simple