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 construct it directly from string literals.

Here's an example:

selectSubstring :: Text -> Maybe Int32 -> Maybe Int32 -> 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 dynamicallyParameterizedStatement.

Instances

Monoid Snippet

Defined in Hasql.DynamicStatements.Snippet.Defs

Methods

mempty :: Snippet

mappend :: Snippet -> Snippet -> Snippet

mconcat :: [Snippet] -> Snippet

Semigroup Snippet

Defined in Hasql.DynamicStatements.Snippet.Defs

Methods

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

sconcat :: NonEmpty Snippet -> Snippet

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

IsString Snippet

Defined in Hasql.DynamicStatements.Snippet.Defs

Methods

fromString :: String -> Snippet

param :: DefaultParamEncoder param => param -> Snippet

Parameter encoded using an implicitly derived encoder from the type.

encoderAndParam :: NullableOrNot Value param -> param -> Snippet

Parameter with an explicitly defined encoder.

sql :: ByteString -> Snippet

SQL chunk in ASCII.