gistfile1.txt

{-# LANGUAGE TemplateHaskell, QuasiQuotes #-}
{-# LANGUAGE TypeFamilies, GADTs, MultiParamTypeClasses #-}
{-# LANGUAGE OverloadedStrings, FlexibleContexts #-}
{-# LANGUAGE EmptyDataDecls #-}

import Database.Persist
import Database.Persist.TH
import Database.Persist.Sqlite
import Data.Text
import Control.Monad.IO.Class

share [mkPersist sqlSettings, mkMigrate "migrateAll"] [persist|
Student
  sid Int
  name Text
  UniqueSID sid
Teacher
  tid Int
  name Text
  UniqueTID tid
Lesson
  name Text
  teacher TeacherId
  totalAvalible Int
  selected Int DEC INC
StudentLesson
  sid StudentId
  lid LessonId
  UniqueST sid lid
|]

main = withSqliteConn ":memory:" $ runSqlConn  $ do
  runMigration migrateAll
  r <- newTeacher 1 "Mike"
  case r of
    Left _ -> liftIO $ print "Error~"
    Right key -> liftIO $ print key


newLesson lid name tid total =
    insertBy $ Lesson lid name tid total

newTeacher tid name = do
    insertBy $ Teacher tid name

newStudent sid name = do
    insertBy $ Student sid name

getLesson lid = selectList [LessonId ==. lid] []

getTeacher tid = selectList [TeacherId ==. tid] []

getStudent sid = selectList [StudentId ==. sid] []

choice tid lid = do
    selectFirst [StudentLessonLid ==. lid]