Thank you for the swift reply, from this example I get the error: 

`PersistEntityBackend' is not a (visible) associated type of class `persistent-0.9.0.4:Database.Persist.Store.PersistEntity'

Which is a new one to me, corrupted or outdated library in my installation perhaps?  I am still running Yesod 1.0, though as this is from the tutorial I doubt this is the issue. 

Best and thanks again.

Chris. 

On Wednesday, 12 September 2012 14:06:36 UTC+1, Felipe Lessa wrote:

On Wed, Sep 12, 2012 at 10:01 AM, Chris Swires <490...-QvkbJbr/y3w2EctHIo1CcQ@public.gmane.org> wrot e:
> Would someone be able to direct me to or provide a basic MySql query
> example? Literally just looking for a self contained connection, query,
> return result to page so that I can adapt this into my project. I've been
> attempting to do this myself but am unfortunately very strapped for time at
> the minute and so any help getting me started would be greatly appreciated.
>
> Thanks for any help in advance.

I didn't test this, but it should work:


{-# LANGUAGE QuasiQuotes, TemplateHaskell, TypeFamilies, OverloadedStrings #-}
{-# LANGUAGE GADTs, FlexibleContexts #-}
import Database.Persist
import Database.Persist.MySQL  -- *
import Database.Persist.TH
import Control.Monad.IO.Class (liftIO)

share [mkPersist sqlSettings, mkMigrate "migrateAll"] [persist|
Person
    name String
    age Int Maybe
    deriving Show
BlogPost
    title String
    authorId PersonId
    deriving Show
|]

main :: IO ()
main = withMySQLConn defaultConnectInfo $ runSqlConn $ do  -- *
    runMigration migrateAll

    johnId <- insert $ Person "John Doe" $ Just 35
    janeId <- insert $ Person "Jane Doe" Nothing

    insert $ BlogPost "My fr1st p0st" johnId
    insert $ BlogPost "One more for good measure" johnId

    oneJohnPost <- selectList [BlogPostAuthorId ==. johnId] [LimitTo 1]
    liftIO $ print (oneJohnPost :: [Entity BlogPost])

    john <- get johnId
    liftIO $ print (john :: Maybe Person)

    delete janeId
    deleteWhere [BlogPostAuthorId ==. johnId]


It's taken from persistent's chapter on the Yesod book.  The only
lines I've changed are marked with "-- *".

Cheers,

--
Felipe.