MYSQL：查询一段时间不使用索引

Database of test:

测试数据库:

SET NAMES utf8;
SET foreign_key_checks = 0;
SET time_zone = '+02:00';
SET sql_mode = 'NO_AUTO_VALUE_ON_ZERO';

CREATE TABLE `account` (
  `idAccount` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(128) NOT NULL,
  PRIMARY KEY (`idAccount`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8; 

CREATE TABLE `users` (
  `idUser` int(11) NOT NULL AUTO_INCREMENT,
  `idAccount` int(11) NOT NULL,
  `firstName` varchar(128) NOT NULL,
  PRIMARY KEY (`idUser`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8;


DROP TABLE IF EXISTS `transactions`;
CREATE TABLE `transactions` (
  `idTransactions` int(11) NOT NULL AUTO_INCREMENT,
  `idUser` int(11) NOT NULL,
  `dateTransaction` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
  PRIMARY KEY (`idTransactions`),
  KEY `index_dateTransaction` (`dateTransaction`) USING BTREE
) ENGINE=MyISAM DEFAULT CHARSET=utf8;


INSERT INTO `transactions` (`idTransactions`, `idUser`, `dateTransaction`) VALUES
(1, 1,  '2012-12-16 15:52:32'),
(2, 1,  '2012-12-20 15:52:37'),
(3, 1,  '2013-02-01 15:52:37'),
(4, 2,  '2013-03-16 15:52:37'),
(5, 2,  '2013-03-18 15:52:37'),
(6, 3,  '2014-04-19 15:52:37'),
(7, 3,  '2014-05-20 15:52:37'),
(8, 4,  '2014-06-21 15:58:46');

INSERT INTO `account` (`idAccount`, `name`) VALUES
(1, 'Burger & Burger');

INSERT INTO `users` (`idUser`, `idAccount`, `firstName` ) VALUES
(1, 1,  'Roberto'),
(2, 1,  'Alessandro');
SET NAMES utf8;
SE