haskelldb-0.12: SQL unwrapper for Haskell. Source code Contents Index

Database.HaskellDB.FieldType Portability non-portable Stability experimental Maintainer haskelldb-users@lists.sourceforge.net

Description

Defines the types of database columns, and functions for converting these between HSQL and internal formats

Synopsis

type FieldDesc = (FieldType, Bool) data FieldType = StringT | IntT | IntegerT | DoubleT | BoolT | CalendarTimeT | BStrT Int toHaskellType :: FieldType -> String class ExprType e where fromHaskellType :: e -> FieldDesc class ExprTypes r where fromHaskellTypes :: r -> [FieldDesc] queryFields :: (ShowLabels r, ExprTypes r) => Query (Rel r) -> [(String, FieldDesc)]

Documentation

type FieldDesc = (FieldType, Bool) Source

The type and nullable flag of a database column

data FieldType Source

A database column type Constructors StringT IntT IntegerT DoubleT BoolT CalendarTimeT BStrT Int Instances Eq FieldType Ord FieldType Read FieldType Show FieldType

toHaskellType :: FieldType -> String Source

class ExprType e where Source

Class which retrieves a field description from a given type. Instances are provided for most concrete types. Instances for Maybe automatically make the field nullable, and instances for all (Expr a) types where a has an ExprType instance allows type information to be recovered from a given column expression. Methods fromHaskellType :: e -> FieldDesc Source Instances ExprType Bool ExprType Double ExprType Int ExprType Integer ExprType String ExprType CalendarTime ExprType a => ExprType (Maybe a) Size n => ExprType (BoundedString n) ExprType a => ExprType (Expr a) ExprType a => ExprType (Rel a)

class ExprTypes r where Source

Class which returns a list of field descriptions. Gets the descriptions of all columns in a Record/query. Most useful when the columns associated with each field in a (Rel r) type must be recovered. Note that this occurs at the type level only and no values are inspected. Methods fromHaskellTypes :: r -> [FieldDesc] Source Instances ExprTypes RecNil ExprTypes r => ExprTypes (Record r) ExprTypes r => ExprTypes (Rel r) (ExprType e, ExprTypes r) => ExprTypes (RecCons f e r)

queryFields :: (ShowLabels r, ExprTypes r) => Query (Rel r) -> [(String, FieldDesc)] Source

Given a query, returns a list of the field names and their types used by the query. Useful for recovering field information once a query has been built up.

Produced by Haddock version 2.6.0