[Haskell-beginners] database access,extracting result...

[Damien Mattei]

just find myself this solution:

main :: IO ()
main =

  do
    conn <- connect defaultConnectInfo
      { connectHost = "moita",
        connectUser = "mattei",
        connectPassword = "****",
        connectDatabase = "sidonie" }

    rows <- query_ conn "select `N° BD` from sidonie.Coordonnées where
Nom = 'A    20'"


    forM_ rows $ \(Only a) ->
      putStrLn $  Text.unpack a

Le 03/12/2018 12:21, Damien Mattei a écrit :
> {-# LANGUAGE OverloadedStrings #-}
> 
> import Database.MySQL.Simple
> import Control.Monad
> import Data.Text as Text
> import Data.Int
> 
> 
> main :: IO ()
> main = do
>   conn <- connect defaultConnectInfo
>     { connectHost = "moita",
>       connectUser = "mattei",
>       connectPassword = "******",
>       connectDatabase = "sidonie" }
> 
>   rows <- query_ conn "select `N° BD` from sidonie.Coordonnées where Nom
> = 'A    20'"
> 
>   --putStrLn $ show rows
> 
>   forM_ rows $ \(fname, lname) ->
>      putStrLn $  fname ++ " " ++ Text.unpack lname ++ " "
> 
> 
> here is the error:
> 
> *Main> :load Toto
> [1 of 1] Compiling Main             ( Toto.hs, interpreted )
> Ok, one module loaded.
> *Main> main
> *** Exception: ConversionFailed {errSQLType = "1 values:
> [(VarString,Just \"-04.3982\")]", errHaskellType = "2 slots in target
> type", errFieldName = "[\"N\\194\\176 BD\"]", errMessage = "mismatch
> between number of columns to convert and number in target type"}
> 
> -04.3982 is the values i want to put in a variable,it's the N° BD
> (Durchmusterung Number)
> 
> 
> ???
> 
> any help greatly appeciated ;-)
> 
> 

-- 
Damien.Mattei at unice.fr, Damien.Mattei at oca.eu, UNS / OCA / CNRS