On 21 June 2011 13:45, David Virebayre <[email protected]> wrote: > The very first example didn't work for me : > ------------------------ > {-# LANGUAGE OverloadedStrings #-} > > import Database.MySQL.Simple > > hello = do > conn <- connect defaultConnectInfo > query conn "select 2 + 2"
Yeah, the first example is wrong. Indeed. Should be fixed. I forgot to tell Bryan about that. I noticed it was wrong when I first looked at it but it's still tripping people up. You can access the docs on a slightly earlier version: http://hackage.haskell.org/package/mysql-simple-0.2.2.0 > Next I modified the simple example to call a stored procedure, it > returns a resultset of 12 columns. > Unfortunately, I realised that QueryResults instances are defined up > to 10 elements only. > However, the documentation shows how to define a QueryResults > instance, so I created a datatype and tried to define the instance, > and got stuck with an error: > > Couldn't match expected type `PlateauSel' > against inferred type `Int -> a' > In the expression: convertError fs vs > In the definition of `convertResults': > convertResults fs vs = convertError fs vs > In the instance declaration for `QueryResults PlateauSel' > > Indeed, the documentation shows that convertError takes 3 parameters, > and I gave, as per the example, only 2. > But I'm not sure what to write for the 3rd parameter, the > documentation doesn't help me here. The doc specifies it here: > convertError :: [Field] -> [Maybe ByteString] -> Int -> a > Throw a ConversionFailed exception, indicating a mismatch between the number > of columns in the Field and row, and the number in the collection to be > converted to. So if you're making an instance for a type that takes ten items from the collection, then put 10. Could always make this clearer. > To try, I put 0, and the test compiled. However, I had a connection > error number 1312, saying my procedure "can't return a result set in > the given context". (The query I used works from the mysql > command-line interface) Ah, I wouldn't know about that, I haven't used the mysql version. _______________________________________________ Haskell-Cafe mailing list [email protected] http://www.haskell.org/mailman/listinfo/haskell-cafe
