Hasql.DynamicStatements.Snippet

Documentation

data Snippet

Composable SQL snippet with parameters injected. Abstracts over placeholders and matching of encoders.

It has an instance of IsString, so having the OverloadedStrings extension enabled you can use string literals to construct it from string.

Here's an example:

selectSubstring :: Text -> Maybe Int64 -> Maybe Int64 -> Snippet
selectSubstring string from to =
  "select substring(" <> param string <>
  foldMap (\ x -> " from " <> param x) from <>
  foldMap (\ x -> " for " <> param x) to <>
  ")"

Having a decoder you can lift it into Statement using dynamicallyParameterized or directly execute it in Session using snippet.

Instances

IsString Snippet

Defined in Hasql.DynamicStatements.Snippet.Defs

Methods

fromString :: String -> Snippet

Semigroup Snippet

Defined in Hasql.DynamicStatements.Snippet.Defs

Methods

(<>) :: Snippet -> Snippet -> Snippet

sconcat :: NonEmpty Snippet -> Snippet

stimes :: Integral b => b -> Snippet -> Snippet

Monoid Snippet

Defined in Hasql.DynamicStatements.Snippet.Defs

Methods

mempty :: Snippet

mappend :: Snippet -> Snippet -> Snippet

mconcat :: [Snippet] -> Snippet

param :: Default (Value param) => param -> Snippet

Parameter encoded using an implicitly derived encoder from the type.

nullableParam :: Default (Value param) => Maybe param -> Snippet

Nullable parameter encoded using an implicitly derived encoder from the type.

encoderAndParam :: Value param -> param -> Snippet

Parameter with an explicitly defined encoder.

encoderAndNullableParam :: Value param -> Maybe param -> Snippet

Nullable parameter with an explicitly defined encoder.