| Safe Haskell | None |
|---|---|
| Language | Haskell2010 |
Database.Beam.Query.CustomSQL
Description
Allows the creation of custom SQL expressions from arbitrary ByteStrings.
Simply create a function with an arbitrary number of ByteString arguments
that returns a ByteString. Then, apply customExpr_ to your function.
This will result in a function with the same arity, that takes in
QGenExprs instead of ByteString's, and returns a QGenExpr as well.
Semantically, the expression builder function is called with arguments
representing SQL expressions, that, when evaluated, will evaluate to the
result of the expressions supplied as arguments to customExpr_. See the
section on extensibility
in the user guide for example usage.
- class IsCustomExprFn fn res | res -> fn where
- valueExpr_ :: QExpr syntax s a -> QExpr syntax s a
- agg_ :: QAgg syntax s a -> QAgg syntax s a
- class (Monoid (CustomSqlSyntax syntax), IsString (CustomSqlSyntax syntax)) => IsCustomSqlSyntax syntax where
- data CustomSqlSyntax syntax :: *
The customExpr_ function
class IsCustomExprFn fn res | res -> fn where Source #
Minimal complete definition
Methods
customExpr_ :: fn -> res Source #
Type-inference help
valueExpr_ :: QExpr syntax s a -> QExpr syntax s a Source #
agg_ :: QAgg syntax s a -> QAgg syntax s a Source #
Force a QGenExpr to be typed as an aggregate. Useful for defining custom
aggregates for use in aggregate_.
For backends
class (Monoid (CustomSqlSyntax syntax), IsString (CustomSqlSyntax syntax)) => IsCustomSqlSyntax syntax where Source #
A type-class for expression syntaxes that can embed custom expressions.
Minimal complete definition
Associated Types
data CustomSqlSyntax syntax :: * Source #
Methods
customExprSyntax :: CustomSqlSyntax syntax -> syntax Source #
Given an arbitrary ByteString, produce a syntax that represents the
ByteString as a SQL expression.
renderSyntax :: syntax -> CustomSqlSyntax syntax Source #
Given an arbitrary syntax, produce a ByteString that corresponds to
how that syntax would look when rendered in the backend.
Instances