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

3 Dec 2018


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