PROCEDURE addNewUserData(IN arg_id BIGINT UNSIGNED, IN arg_data VARCHAR(255))
BEGIN
  --уникальны по id пользователя
  INSERT IGNORE INTO users (idUser, `data`)
    VALUES (arg_id, arg_data);
  IF ROW_COUNT() = 0 THEN
    INSERT INTO reservedData (`data`, `lock`) VALUES (arg_data, 0);
  END IF;
  SELECT u.`data` FROM users u WHERE u.idUser = arg_id;
END

PROCEDURE getUserDataById(IN arg_id BIGINT)
BEGIN
  DECLARE lockValue bigint;
  IF NOT EXISTS (SELECT 1 FROM users u WHERE u.idUser = arg_id) THEN
    UPDATE sequence SET id = LAST_INSERT_ID(id + 1) WHERE type = 1;
    set lockValue:= LAST_INSERT_ID();
    START TRANSACTION;
      UPDATE reservedData a SET `lock` = lockValue WHERE `lock` = 0 LIMIT 1;
      INSERT IGNORE INTO users (idUser, `data`) 
        SELECT arg_id, a.`data` FROM reservedData a
          WHERE a.`lock` = lockValue;
      IF ROW_COUNT() = 0 THEN
        UPDATE reservedData a SET `lock` = 0 WHERE `lock` = lockValue;
      ELSE
        DELETE FROM reservedData WHERE `lock` = lockValue;
      END IF;
    COMMIT;
  END IF;
  SELECT u.`data` AS `data` FROM users u WHERE u.idUser = arg_id;
END