Squeal.PostgreSQL.Expression.Parameter

out-of-line parameters

Parameter

class KnownNat n => HasParameter (n :: Nat) (params :: [NullType]) (ty :: NullType) | n params -> ty where

A HasParameter constraint is used to indicate a value that is supplied externally to a SQL statement. manipulateParams, queryParams and traversePrepared support specifying data values separately from the SQL command string, in which case params are used to refer to the out-of-line data values.

Minimal complete definition

Nothing

Methods

parameter :: TypeExpression db ty -> Expression grp lat with db params from ty

parameter takes a Nat using type application and a TypeExpression.

>>> printSQL (parameter @1 int4)
($1 :: int4)

Instances

(KnownNat n, HasParameter (n - 1) xs x, params ~ (y ': xs)) => HasParameter n params x

Defined in Squeal.PostgreSQL.Expression.Parameter

Methods

parameter :: TypeExpression db x -> Expression grp lat with db params from x

params ~ (x ': xs) => HasParameter 1 params x

Defined in Squeal.PostgreSQL.Expression.Parameter

Methods

parameter :: TypeExpression db x -> Expression grp lat with db params from x

param

Arguments

:: (NullTyped db ty, HasParameter n params ty)

=> Expression grp lat with db params from ty

param

param takes a Nat using type application and for basic types, infers a TypeExpression.

>>> printSQL (param @1 @('Null 'PGint4))
($1 :: int4)