Database.SQLite.Simple.Types

Top-level module for sqlite-simple.

Documentation

data Null

A placeholder for the SQL NULL value.

Constructors

Null

Instances

Eq Null

Read Null

Show Null

FromField Null

ToField Null

Typeable * Null

newtype Only a

A single-value "collection".

This is useful if you need to supply a single parameter to a SQL query, or extract a single column from a SQL result.

Parameter example:

query c "select x from scores where x > ?" (Only (42::Int))

Result example:

xs <- query_ c "select id from users"
forM_ xs $ \(Only id) -> {- ... -}

Constructors

Only

Fields

fromOnly :: a

Instances

Functor Only

Eq a => Eq (Only a)

Ord a => Ord (Only a)

Read a => Read (Only a)

Show a => Show (Only a)

FromField a => FromRow (Only a)

ToField a => ToRow (Only a)

Typeable (* -> *) Only

newtype Query

A query string. This type is intended to make it difficult to construct a SQL query by concatenating string fragments, as that is an extremely common way to accidentally introduce SQL injection vulnerabilities into an application.

This type is an instance of IsString, so the easiest way to construct a query is to enable the OverloadedStrings language extension and then simply write the query in double quotes.

{-# LANGUAGE OverloadedStrings #-}

import Database.SQLite.Simple

q :: Query
q = "select ?"

The underlying type is a Text, and literal Haskell strings that contain Unicode characters will be correctly transformed to UTF-8.

Constructors

Query

Fields

fromQuery :: Text

Instances

Eq Query

Ord Query

Read Query

Show Query

IsString Query

Monoid Query

Typeable * Query

data h :. t infixr 3

A composite type to parse your custom data structures without having to define dummy newtype wrappers every time.

instance FromRow MyData where ...

instance FromRow MyData2 where ...

then I can do the following for free:

res <- query' c "..."
forM res $ \(MyData{..} :. MyData2{..}) -> do
  ....

Constructors

h :. t infixr 3

Instances

(Eq h, Eq t) => Eq ((:.) h t)

(Ord h, Ord t) => Ord ((:.) h t)

(Read h, Read t) => Read ((:.) h t)

(Show h, Show t) => Show ((:.) h t)

(FromRow a, FromRow b) => FromRow ((:.) a b)

(ToRow a, ToRow b) => ToRow ((:.) a b)

Typeable (* -> * -> *) (:.)