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README
sql-simple
common middle-level sql client.
tutorial
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE ConstraintKinds #-}
import Control.Applicative
import Database.Sql.Simple
import Database.Sql.Simple.SQLite
import Database.Sql.Simple.PostgreSQL
import Database.Sql.Simple.Pool
-- you must specify 1st type variable of Sql Monad.
-- by explicit type signature,
testQuery :: (ToRow conn (Only Int), FromRow conn (Only Int), Backend conn)
=> conn -> Sql '[SQLite, PostgreSQL] [Int]
testQuery c = do
execute_ c "CREATE TABLE test (id int)"
execute c "INSERT INTO test VALUES (?)" (Only (1 :: Int))
map fromOnly <$> query_ c "SELECT * FROM test"
-- or sql function(testQuery' equivalent to testQuery).
testQuery' c = sql (sqlite +:+ postgreSQL) $ do
execute_ c "CREATE TABLE test (id int)"
execute c "INSERT INTO test VALUES (?)" (Only (1 :: Int))
i <- map fromOnly <$> query_ c "SELECT * FROM test"
return (i :: [Int])
-- you can specify backend specific Query.
specificQuery :: Backend conn => conn -> Sql '[SQLite, PostgreSQL] ()
specificQuery c =
execute_ c (specify sqlite "[sqlite query]" "[common query]")
main :: IO ()
main = do
-- l <- withConnection ("test.sqlite3" :: ConnectInfo SQLite) testQuery
l <- withConnection (ConnectionPool def "test.sqlite3" :: ConnectInfo (Pool SQLite)) testQuery
-- l <- withConnection (def :: ConnectInfo PostgreSQL) testQuery
print l