Model.hs

{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE MultiParamTypeClasses #-}

module Model where

import Data.Int (Int32)

import Data.Time

import Database.HDBC.Record.Persistable ()
import Database.Relational.Query (defaultConfig)
import Database.Relational.Query.TH (defineTableDefault)


$(defineTableDefault defaultConfig "TEST" "person"
  [ ("name",         [t| String |])
  , ("nickname",     [t| String |])
  , ("day" ,         [t| Day  |])
  , ("sex" ,         [t| Int32 |])
  ] [] [0] $ Just 0)

OrPlaceholders.hs

module OrPlaceholders where

import Data.String (IsString)
import Language.SQL.Keyword (Keyword (LIKE))
import qualified Language.SQL.Keyword as SQL
import Database.Relational.Query

import Model (Person, person)
import qualified Model as Person


like :: (SqlProjectable p, ProjectableShowSql p, IsString a)
     => p a -> p b -> p (Maybe Bool)
like =  unsafeBinOp (SQL.defineBinOp LIKE)

findOr :: Relation (String, String) Person
findOr =  relation' $ do
  p   <- query person
  (ph, ()) <- placeholder $ \pph -> wheres
    $ p ! Person.name' .=. pph ! fst' `or'` p ! Person.nickname' .=. pph ! snd'
  return (ph, p)