Portability	unknown
Stability	experimental
Maintainer	[email protected]
Safe Haskell	None

Database.Relational.Query.Expr

Contents

Typed SQL Expression
Type conversion

Description

This module defines phantom typed SQL expression object. Contains normal interfaces.

Synopsis

Typed SQL Expression

data Expr p a Source

Phantom typed SQL expression object. Project from projection type p.

Instances

ProjectableMaybe (Expr p)	Control phantom `Maybe` type in SQL expression type `Expr`.
ProjectableShowSql (Expr p)	Unsafely get SQL term from `Expr`.
SqlProjectable (Expr p)	Unsafely make `Expr` from SQL terms.
Show (Expr p a)	Show expression.

valueExpr :: ShowConstantTermsSQL ft => ft -> Expr p ftSource

Typed constant SQL expression from Haskell value.

Type conversion

just :: Expr p ft -> Expr p (Maybe ft)Source

Convert phantom type into Maybe.

fromJust :: Expr p (Maybe ft) -> Expr p ftSource

Allowed only for having or where Expr. So NULL expression result will be possible. Behavior around boolean is strongly dependent on RDBMS impelemetations.

exprAnd :: Expr p Bool -> Expr p Bool -> Expr p Bool Source

AND operator for Expr.