mysql-simple-0.4.0.1: A mid-level MySQL client library.

Copyright(c) 2011 MailRank Inc.
LicenseBSD3
MaintainerPaul Rouse <pyr@doynton.org>
Stabilityexperimental
Portabilityportable
Safe HaskellNone
LanguageHaskell98

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 Double type is compatible with the MySQL Long type because it can represent a Long exactly. On the other hand, since a Double might lose precision if representing a LongLong, the two are not considered compatible.

Synopsis

Documentation

class Result a where #

A type that may be converted from a SQL type.

Minimal complete definition

convert

Methods

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

Convert a SQL value to a Haskell value.

Throws a ResultError if conversion fails.

Instances

Result Bool # 
Result Double # 
Result Float # 
Result Int # 

Methods

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

Result Int8 # 
Result Int16 # 
Result Int32 # 
Result Int64 # 
Result Integer # 
Result Word # 
Result Word8 # 
Result Word16 # 
Result Word32 # 
Result Word64 # 
Result ByteString # 
Result ByteString # 
Result Text # 
Result Text # 
Result TimeOfDay # 
Result UTCTime # 
Result Day # 

Methods

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

Result [Char] # 

Methods

convert :: Field -> Maybe ByteString -> [Char] #

Result a => Result (Maybe a) # 

Methods

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

Result (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.

UnexpectedNull

A SQL NULL was encountered when the Haskell type did not permit it.

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).