使用HaskellDB取消映射表记录的基本示例

import Database.HaskellDB

-- 定义一个表
data Person = Person { name :: String, age :: Int }
instance Record Person where
  recordName _ = "person"

-- 定义一个删除记录的函数
deletePerson :: String -> Int -> Query Person
deletePerson name age = do
  person <- table "person"
  restrict (person!name .==. constant name .&&. person!age .==. constant age)
  return person

-- 执行删除操作
main :: IO ()
main = do
  let conn = connect "dbname=mydb user=myuser password=mypassword"
  let query = deletePerson "John Doe" 30
  result <- queryExec conn (delete query)
  putStrLn $ "Deleted " ++ show (length result) ++ " records."