Copyright	(c) 2011 MailRank Inc.
License	BSD3
Maintainer	Paul Rouse <pyr@doynton.org>
Stability	experimental
Portability	portable
Safe Haskell	None
Language	Haskell98

Database.MySQL.Simple.Result

Description

The Result typeclass, for converting a single value in a row returned by a SQL query into a more useful Haskell representation.

A Haskell numeric type is considered to be compatible with all MySQL numeric types that are less accurate than it. For instance, the Haskell Type type is compatible with the MySQL Long type because it can represent a Long exactly. On the other hand, since a Type might lose precision if representing a LongLong, the two are not considered compatible.

Synopsis

class Result a where
- convert :: Field -> Maybe ByteString -> a
data ResultError
- = Incompatible {
  - errSQLType :: String
  - errHaskellType :: String
  - errFieldName :: String
  - errMessage :: String
  }
- | UnexpectedNull {
  - errSQLType :: String
  - errHaskellType :: String
  - errFieldName :: String
  - errMessage :: String
  }
- | ConversionFailed {
  - errSQLType :: String
  - errHaskellType :: String
  - errFieldName :: String
  - errMessage :: String
  }

Documentation

class Result a where #

A type that may be converted from a SQL type.

Methods

convert :: Field -> Maybe ByteString -> a #

Convert a SQL value to a Haskell value.

Throws a ResultError if conversion fails.

Instances

Result Bool #
Instance details Defined in Database.MySQL.Simple.Result Methods convert :: Field -> Maybe ByteString -> Bool #
Result Double #
Instance details Defined in Database.MySQL.Simple.Result Methods convert :: Field -> Maybe ByteString -> Double #
Result Float #
Instance details Defined in Database.MySQL.Simple.Result Methods convert :: Field -> Maybe ByteString -> Float #
Result Int #
Instance details Defined in Database.MySQL.Simple.Result Methods convert :: Field -> Maybe ByteString -> Int #
Result Int8 #
Instance details Defined in Database.MySQL.Simple.Result Methods convert :: Field -> Maybe ByteString -> Int8 #
Result Int16 #
Instance details Defined in Database.MySQL.Simple.Result Methods convert :: Field -> Maybe ByteString -> Int16 #
Result Int32 #
Instance details Defined in Database.MySQL.Simple.Result Methods convert :: Field -> Maybe ByteString -> Int32 #
Result Int64 #
Instance details Defined in Database.MySQL.Simple.Result Methods convert :: Field -> Maybe ByteString -> Int64 #
Result Integer #
Instance details Defined in Database.MySQL.Simple.Result Methods convert :: Field -> Maybe ByteString -> Integer #
Result Word #
Instance details Defined in Database.MySQL.Simple.Result Methods convert :: Field -> Maybe ByteString -> Word #
Result Word8 #
Instance details Defined in Database.MySQL.Simple.Result Methods convert :: Field -> Maybe ByteString -> Word8 #
Result Word16 #
Instance details Defined in Database.MySQL.Simple.Result Methods convert :: Field -> Maybe ByteString -> Word16 #
Result Word32 #
Instance details Defined in Database.MySQL.Simple.Result Methods convert :: Field -> Maybe ByteString -> Word32 #
Result Word64 #
Instance details Defined in Database.MySQL.Simple.Result Methods convert :: Field -> Maybe ByteString -> Word64 #
Result ByteString #
Instance details Defined in Database.MySQL.Simple.Result Methods convert :: Field -> Maybe ByteString -> ByteString #
Result ByteString #
Instance details Defined in Database.MySQL.Simple.Result Methods convert :: Field -> Maybe ByteString0 -> ByteString #
Result Text #
Instance details Defined in Database.MySQL.Simple.Result Methods convert :: Field -> Maybe ByteString -> Text #
Result Text #
Instance details Defined in Database.MySQL.Simple.Result Methods convert :: Field -> Maybe ByteString -> Text #
Result TimeOfDay #
Instance details Defined in Database.MySQL.Simple.Result Methods convert :: Field -> Maybe ByteString -> TimeOfDay #
Result UTCTime #
Instance details Defined in Database.MySQL.Simple.Result Methods convert :: Field -> Maybe ByteString -> UTCTime #
Result Day #
Instance details Defined in Database.MySQL.Simple.Result Methods convert :: Field -> Maybe ByteString -> Day #
Result [Char] #
Instance details Defined in Database.MySQL.Simple.Result Methods convert :: Field -> Maybe ByteString -> [Char] #
Result a => Result (Maybe a) #
Instance details Defined in Database.MySQL.Simple.Result Methods convert :: Field -> Maybe ByteString -> Maybe a #
Result (Ratio Integer) #
Instance details Defined in Database.MySQL.Simple.Result Methods convert :: Field -> Maybe ByteString -> Ratio Integer #

data ResultError #

Exception thrown if conversion from a SQL value to a Haskell value fails.

Constructors

Incompatible	The SQL and Haskell types are not compatible.
Fields errSQLType :: String errHaskellType :: String errFieldName :: String errMessage :: String
UnexpectedNull	A SQL `NULL` was encountered when the Haskell type did not permit it.
Fields errSQLType :: String errHaskellType :: String errFieldName :: String errMessage :: String
ConversionFailed	The SQL value could not be parsed, or could not be represented as a valid Haskell value, or an unexpected low-level error occurred (e.g. mismatch between metadata and actual data in a row).
Fields errSQLType :: String errHaskellType :: String errFieldName :: String errMessage :: String

Instances

Eq ResultError #
Instance details Defined in Database.MySQL.Simple.Result Methods (==) :: ResultError -> ResultError -> Bool # (/=) :: ResultError -> ResultError -> Bool #
Show ResultError #
Instance details Defined in Database.MySQL.Simple.Result Methods showsPrec :: Int -> ResultError -> ShowS # show :: ResultError -> String # showList :: [ResultError] -> ShowS #
Exception ResultError #
Instance details Defined in Database.MySQL.Simple.Result Methods toException :: ResultError -> SomeException # fromException :: SomeException -> Maybe ResultError # displayException :: ResultError -> String #