php - 使用分页(PHP、MySQL)时计算运行总计/余额的最有效方法是什么

Question

我有一个 MySQL 表，用于存储员工记录的里程记录。我有一个 PHP 页面，它在表中输出每个员工的里程记录(从最新到最旧)以及运行余额。这一切都运行良好。

里程记录的增长速度超出预期，现在很明显需要分页。我已经编写了分页程序，效果很好。我现在遇到的问题是分页已经“破坏”了运行平衡，因为它忽略了我选择的记录之外的任何值。例如，假设您的银行帐户刚刚提供了 7 月份的余额，而没有考虑您帐户 6 月份的余额。

关于如何在理论上解决这个问题的建议(我不需要逐行代码)将非常感激，因为 Google 没有提供太多帮助。

编辑 1

Database and data

-- phpMyAdmin SQL Dump
-- version 4.0.10.14
-- http://www.phpmyadmin.net
--
-- Host: localhost:3306
-- Generation Time: Jul 21, 2016 at 07:11 PM
-- Server version: 5.1.73-cll
-- PHP Version: 5.4.31

SET SQL_MODE = "NO_AUTO_VALUE_ON_ZERO";
SET time_zone = "+00:00";

--
-- Database: `propsyst_main`
--

-- --------------------------------------------------------

--
-- Table structure for table `employee_mileage`
--

CREATE TABLE IF NOT EXISTS `employee_mileage` (
  `employee_mileage_id` int(11) NOT NULL AUTO_INCREMENT,
  `employee_mileage_employee_id` int(11) DEFAULT NULL,
  `employee_mileage_vehicle_id` smallint(6) DEFAULT NULL,
  `employee_mileage_start_postcode` varchar(8) COLLATE utf8_bin DEFAULT NULL,
  `employee_mileage_end_postcode` varchar(8) COLLATE utf8_bin DEFAULT NULL,
  `employee_mileage_mileage` decimal(6,2) DEFAULT NULL,
  PRIMARY KEY (`employee_mileage_id`)
) ENGINE=MyISAM  DEFAULT CHARSET=utf8 COLLATE=utf8_bin AUTO_INCREMENT=8 ;

--
-- Dumping data for table `employee_mileage`
--

INSERT INTO `employee_mileage` (`employee_mileage_id`, `employee_mileage_employee_id`, `employee_mileage_vehicle_id`, `employee_mileage_start_postcode`, `employee_mileage_end_postcode`, `employee_mileage_mileage`) VALUES
(1, 1, 2, 'L17 0BZ', 'L36 9TJ', '1.00'),
(2, 1, 2, 'L17 0BZ', 'L36 9TJ', '2.00'),
(3, 1, 2, 'L17 0BZ', 'L36 9TJ', '3.00'),
(4, 1, 2, 'L17 0BZ', 'L36 9TJ', '4.00'),
(5, 1, 2, 'L17 0BZ', 'L36 9TJ', '5.00'),
(6, 1, 2, 'L17 0BZ', 'L36 9TJ', '6.00'),
(7, 1, 2, 'L17 0BZ', 'L36 9TJ', '7.00');

编辑2

查询尝试不起作用；

$statement = "SELECT *
from (
        SELECT     em.*, e.*,
                   @balance := @balance + em.employee_mileage_mileage as balance
        FROM       employee_mileage em
        CROSS JOIN (select   @balance := 0) init
        INNER JOIN employee e
on em.employee_mileage_employee_id = e.employee_id
        where      em.employee_mileage_employee_id = " . $employee_id . "
        order by   em.employee_mileage_id
        ) as base
ORDER BY   em.employee_mileage_id DESC";

$employee_mileage_query = mysqli_query($con,"{$statement} LIMIT {$startpoint} , {$per_page}") or die(mysql_error());

编辑3

数据库；

-- phpMyAdmin SQL Dump
-- version 4.0.10.14
-- http://www.phpmyadmin.net
--
-- Host: localhost:3306
-- Generation Time: Jul 25, 2016 at 10:22 PM
-- Server version: 5.1.73-cll
-- PHP Version: 5.4.31

SET SQL_MODE = "NO_AUTO_VALUE_ON_ZERO";
SET time_zone = "+00:00";

--
-- Database: `propsyst_main`
--

-- --------------------------------------------------------

--
-- Table structure for table `employee_mileage`
--

CREATE TABLE IF NOT EXISTS `employee_mileage` (
  `employee_mileage_id` int(11) NOT NULL AUTO_INCREMENT,
  `employee_mileage_employee_id` int(11) DEFAULT NULL,
  `employee_mileage_vehicle_id` smallint(6) DEFAULT NULL,
  `employee_mileage_journey_date` date DEFAULT NULL,
  `employee_mileage_start_postcode` varchar(8) COLLATE utf8_bin DEFAULT NULL,
  `employee_mileage_end_postcode` varchar(8) COLLATE utf8_bin DEFAULT NULL,
  `employee_mileage_mileage` decimal(6,2) DEFAULT NULL,
  `employee_mileage_date_created` datetime DEFAULT NULL,
  `employee_mileage_created_by` int(11) DEFAULT NULL,
  PRIMARY KEY (`employee_mileage_id`)
) ENGINE=MyISAM  DEFAULT CHARSET=utf8 COLLATE=utf8_bin AUTO_INCREMENT=7 ;

--
-- Dumping data for table `employee_mileage`
--

INSERT INTO `employee_mileage` (`employee_mileage_id`, `employee_mileage_employee_id`, `employee_mileage_vehicle_id`, `employee_mileage_journey_date`, `employee_mileage_start_postcode`, `employee_mileage_end_postcode`, `employee_mileage_mileage`, `employee_mileage_date_created`, `employee_mileage_created_by`) VALUES
(1, 32, 1, '2016-07-15', 'L17 0BZ', 'L6 5BJ', '4.19', '2016-07-25 10:15:01', 32),
(2, 32, 1, '2016-07-15', 'L6 5BJ', 'L17 0BZ', '4.19', '2016-07-25 10:15:01', 32),
(5, 32, 1, '2016-07-23', 'L17 0BZ', 'L17 1AE', '1.55', '2016-07-25 12:14:15', 32),
(3, 32, 1, '2016-07-21', 'L17 0BZ', 'L19 0PD', '2.03', '2016-07-25 12:09:24', 32),
(4, 32, 1, '2016-07-21', 'L19 0PD', 'L17 0BZ', '2.03', '2016-07-25 12:09:24', 32),
(6, 32, 1, '2016-07-23', 'L17 1AE', 'L17 0BZ', '1.55', '2016-07-25 12:14:15', 32);

查询；

$statement = "SELECT *
from (
        SELECT     em.*, e.*, v.*,
                   @balance := @balance + em.employee_mileage_mileage as balance
        FROM       employee_mileage em
        CROSS JOIN (select @balance := 0) init
        INNER JOIN employee e
        on em.employee_mileage_employee_id = e.employee_id
        INNER JOIN vehicle v
        on em.employee_mileage_vehicle_id = v.vehicle_id
        WHERE      em.employee_mileage_employee_id = " . $employee_id . "
        ORDER BY   em.employee_mileage_id
        ) as base
ORDER BY base.employee_mileage_id DESC";

$employee_mileage_query = mysqli_query($con,"{$statement} LIMIT {$startpoint} , {$per_page}") or die(mysql_error());

输出；

Answer 1

我建议计算 SQL 查询中的运行余额。

以下是该 SQL 语句的示例:

SELECT *
from (
        SELECT     *,
                   @balance := @balance + em.employee_mileage_mileage as balance
        FROM       (select     em.*, e.*, v.*
                    from       employee_mileage em
                    INNER JOIN employee e
                            on em.employee_mileage_employee_id = e.employee_id
                    INNER JOIN vehicle v
                            on em.employee_mileage_vehicle_id = v.vehicle_id
                    WHERE      em.employee_mileage_employee_id = ?
                    ORDER BY   em.employee_mileage_id ASC
                    ) em
        CROSS JOIN (select @balance := 0) init
        ) as base
ORDER BY base.employee_mileage_id DESC
LIMIT   ?, 2

上述语句中的参数(用?标记)应绑定(bind)到:

• 您想要显示其数据的employee_id
• 当前页面的起始行(从零开始)

内部查询遍历该特定员工的所有行，并将运行余额添加到每条记录中。然后，外部查询反转排序顺序并对其应用限制以实现分页目的。

这个解决方案不需要在 PHP 中进行计算；运行余额在查询结果集中很容易获得，并且在每个页面上都是正确的。

这是一个小SQL fiddle演示如何从总共 6 行中获取第二页，每页 2 行，包括正确的余额。