Hi, i have this query in SQL used by my Haskell code: let name = "A 20" -- return the list of N°BD from WDS for a given name let qry_head_WDS = "select DNUM from WDS where DISC = ?" :: Query putStrLn "before query WDS" bd_rows_WDS <- query conn qry_head_WDS (Only (name::String)) putStrLn "after query WDS" forM_ bd_rows_WDS $ \(Only a) -> putStrLn $ Text.unpack a works well if there is no NULL values in a database, but if NULL value for field N°BD i got this exception at runtime: before query WDS *** Exception: UnexpectedNull {errSQLType = "String", errHaskellType = "Text", errFieldName = "DNUM", errMessage = "unexpected null in table WDS of database sidonie"} *Main> i need some code ,perheaps uing Maybe to handle the NULL value in the field N°BD i think Haskell have special feature to program this , i read the article: https://lukeplant.me.uk/blog/posts/null-pointers-vs-none-vs-maybe/ but for now i have no concrete solution.... Regards, Damien -- Damien.Mattei@unice.fr, Damien.Mattei@oca.eu, UNS / OCA / CNRS