search
HomeDatabaseMysql Tutorial分页显示详解_MySQL

分页显示详解_MySQL

Jun 01, 2016 pm 02:05 PM
elseifpagesqlshowresultDetailed explanation

1、前言

分页显示是一种非常常见的浏览和显示大量数据的方法,属于web编程中最常处理的事件之一。对于web编程的老手来说,编写这种代码实在是和呼吸一样自然,但是对于初学者来说,常常对这个问题摸不着头绪,因此特地撰写此文对这个问题进行详细的讲解,力求让看完这篇文章的朋友在看完以后对于分页显示的原理和实现方法有所了解。本文适合初学者阅读,所有示例代码均使用php编写。

2、原理

所谓分页显示,也就是将数据库中的结果集人为的分成一段一段的来显示,这里需要两个初始的参数:

每页多少条记录($PageSize)?
当前是第几页($CurrentPageID)?

现在只要再给我一个结果集,我就可以显示某段特定的结果出来。
至于其他的参数,比如:上一页($PreviousPageID)、下一页($NextPageID)、总页数($numPages)等等,都可以根据前边这几个东西得到。
以mysql数据库为例,如果要从表内截取某段内容,sql语句可以用:select * from table limit offset, rows。看看下面一组sql语句,尝试一下发现其中的规率。

前10条记录:select * from table limit 0,10
第11至20条记录:select * from table limit 10,10
第21至30条记录:select * from table limit 20,10
……

这一组sql语句其实就是当$PageSize=10的时候取表内每一页数据的sql语句,我们可以总结出这样一个模板:

select * from table limit ($CurrentPageID - 1) * $PageSize, $PageSize

拿这个模板代入对应的值和上边那一组sql语句对照一下看看是不是那么回事。搞定了最重要的如何获取数据的问题以后,剩下的就仅仅是传递参数,构造合适的sql语句然后使用php从数据库内获取数据并显示了。以下我将用具体代码加以说明。

3、简单代码
请详细阅读以下代码,自己调试运行一次,最好把它修改一次,加上自己的功能,比如搜索等等。

// 建立数据库连接
$link = mysql_connect("localhost", "mysql_user", "mysql_password")
      or die("Could not connect: " . mysql_error());
// 获取当前页数
if( isset($_GET['page']) ){
   $page = intval( $_GET['page'] );
}
else{
   $page = 1;
}
// 每页数量
$PageSize = 10;
// 获取总数据量
$sql = "select count(*) as amount from table";
$result = mysql_query($sql);
$row = mysql_fetch_row($result);
$amount = $row['amount'];
// 记算总共有多少页
if( $amount ){
   if( $amount    if( $amount % $page_size ){                                  //取总数据量除以每页数的余数
       $page_count = (int)($amount / $page_size) + 1;           //如果有余数,则页数等于总数据量除以每页数的结果取整再加一
   }else{
       $page_count = $amount / $page_size;                      //如果没有余数,则页数等于总数据量除以每页数的结果
   }
}
else{
   $page_count = 0;
}

// 翻页链接
$page_string = '';
if( $page == 1 ){
   $page_string .= '第一页|上一页|';
}
else{
   $page_string .= '第一页|上一页|';
}
if( ($page == $page_count) || ($page_count == 0) ){
   $page_string .= '下一页|尾页';
}
else{
   $page_string .= '下一页|尾页';
}
// 获取数据,以二维数组格式返回结果
if( $amount ){
   $sql = "select * from table order by id desc limit ". ($page-1)*$page_size .", $page_size";
   $result = mysql_query($sql);
  
   while ( $row = mysql_fetch_row($result) ){
       $rowset[] = $row;
   }
}else{
   $rowset = array();
}
// 没有包含显示结果的代码,那不在讨论范围,只要用foreach就可以很简单的用得到的二维数组来显示结果
?>


4、OO风格代码
以下代码中的数据库连接是使用的pear db类进行处理

// FileName: Pager.class.php
// 分页类,这个类仅仅用于处理数据结构,不负责处理显示的工作
Class Pager
{
   var $PageSize;             //每页的数量
   var $CurrentPageID;        //当前的页数
   var $NextPageID;           //下一页
   var $PreviousPageID;       //上一页
   var $numPages;             //总页数
   var $numItems;             //总记录数
   var $isFirstPage;          //是否第一页
   var $isLastPage;           //是否最后一页
   var $sql;                  //sql查询语句
   
  function Pager($option)
   {
       global $db;
       $this->_setOptions($option);
       // 总条数
       if ( !isset($this->numItems) )
       {
           $res = $db->query($this->sql);
           $this->numItems = $res->numRows();
       }
       // 总页数
       if ( $this->numItems > 0 )
       {
           if ( $this->numItems PageSize ){ $this->numPages = 1; }
           if ( $this->numItems % $this->PageSize )
           {
               $this->numPages= (int)($this->numItems / $this->PageSize) + 1;
           }
           else
           {
               $this->numPages = $this->numItems / $this->PageSize;
           }
       }
       else
       {
           $this->numPages = 0;
       }
       
       switch ( $this->CurrentPageID )
       {
           case $this->numPages == 1:
               $this->isFirstPage = true;
               $this->isLastPage = true;
               break;
           case 1:
               $this->isFirstPage = true;
               $this->isLastPage = false;
               break;
           case $this->numPages:
               $this->isFirstPage = false;
               $this->isLastPage = true;
               break;
           default:
               $this->isFirstPage = false;
               $this->isLastPage = false;
       }
      
       if ( $this->numPages > 1 )
       {
           if ( !$this->isLastPage ) { $this->NextPageID = $this->CurrentPageID + 1; }
           if ( !$this->isFirstPage ) { $this->PreviousPageID = $this->CurrentPageID - 1; }
       }
      
       return true;
   }
  
   /***
    *
    * 返回结果集的数据库连接
    * 在结果集比较大的时候可以直接使用这个方法获得数据库连接,然后在类之外遍历,这样开销较小
    * 如果结果集不是很大,可以直接使用getPageData的方式获取二维数组格式的结果
    * getPageData方法也是调用本方法来获取结果的
    *
    ***/
  
   function getDataLink()
   {
       if ( $this->numItems )
       {
           global $db;
          
           $PageID = $this->CurrentPageID;
          
           $from = ($PageID - 1)*$this->PageSize;
           $count = $this->PageSize;
           $link = $db->limitQuery($this->sql, $from, $count);   //使用Pear DB::limitQuery方法保证数据库兼容性
          
           return $link;
       }
       else
       {
           return false;
       }
   }
  
   /***
    *
    * 以二维数组的格式返回结果集
    *
    ***/
  
   function getPageData()
   {
       if ( $this->numItems )
       {
           if ( $res = $this->getDataLink() )
           {      
               if ( $res->numRows() )
               {
                   while ( $row = $res->fetchRow() )
                   {
                       $result[] = $row;
                   }
               }
               else
               {
                   $result = array();
               }
              
               return $result;
           }
           else
           {
               return false;
           }
       }
       else
       {
           return false;
       }
   }
  
   function _setOptions($option)
   {
       $allow_options = array(
                   'PageSize',
                   'CurrentPageID',
                   'sql',
                   'numItems'
       );
      
       foreach ( $option as $key => $value )
       {
           if ( in_array($key, $allow_options) && ($value != null) )
           {
               $this->$key = $value;
           }
       }
      
       return true;
   }
}
?>

// FileName: test_pager.php
// 这是一段简单的示例代码,前边省略了使用pear db类建立数据库连接的代码
require "Pager.class.php";
if ( isset($_GET['page']) )
{
   $page = (int)$_GET['page'];
}
else
{
   $page = 1;
}
$sql = "select * from table order by id";
$pager_option = array(
       "sql" => $sql,
       "PageSize" => 10,
       "CurrentPageID" => $page
);
if ( isset($_GET['numItems']) )
{
   $pager_option['numItems'] = (int)$_GET['numItems'];
}
$pager = @new Pager($pager_option);
$data = $pager->getPageData();
if ( $pager->isFirstPage )
{
   $turnover = "首页|上一页|";
}
else
{
   $turnover = "首页|上一页|";
}
if ( $pager->isLastPage )
{
   $turnover .= "下一页|尾页";
}
else
{
   $turnover .= "下一页|尾页";
}
?>
 


需要说明的地方有两个:

这个类仅仅处理数据,并不负责处理显示,因为我觉得将数据的处理和结果的显示都放到一个类里边实在是有些勉强。显示的时候情况和要求多变,不如自己根据类给出的结果处理,更好的方法是根据这个Pager类继承一个自己的子类来显示不同的分页,比如显示用户分页列表可以:

Class MemberPager extends Pager
{
   function showMemberList()
   {
       global $db;
      
       $data = $this->getPageData();
// 显示结果的代码
       // ......
   }
}
/// 调用
if ( isset($_GET['page']) )
{
   $page = (int)$_GET['page'];
}
else
{
   $page = 1;
}
$sql = "select * from members order by id";
$pager_option = array(
       "sql" => $sql,
       "PageSize" => 10,
       "CurrentPageID" => $page
);
if ( isset($_GET['numItems']) )
{
   $pager_option['numItems'] = (int)$_GET['numItems'];
}
$pager = @new MemberPager($pager_option);
$pager->showMemberList();
?>
 


第二个需要说明的地方就是不同数据库的兼容性,在不同的数据库里截获一段结果的写法是不一样的。
mysql: select * from table limit offset, rows
pgsql: select * from table limit m offset n
......
所以要在类里边获取结果的时候需要使用pear db类的limitQuery方法。

ok,写完收功,希望花时间看完这些文字的你不觉得是浪费了时间。

Statement
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
How does MySQL differ from PostgreSQL?How does MySQL differ from PostgreSQL?Apr 29, 2025 am 12:23 AM

MySQLisbetterforspeedandsimplicity,suitableforwebapplications;PostgreSQLexcelsincomplexdatascenarioswithrobustfeatures.MySQLisidealforquickprojectsandread-heavytasks,whilePostgreSQLispreferredforapplicationsrequiringstrictdataintegrityandadvancedSQLf

How does MySQL handle data replication?How does MySQL handle data replication?Apr 28, 2025 am 12:25 AM

MySQL processes data replication through three modes: asynchronous, semi-synchronous and group replication. 1) Asynchronous replication performance is high but data may be lost. 2) Semi-synchronous replication improves data security but increases latency. 3) Group replication supports multi-master replication and failover, suitable for high availability requirements.

How can you use the EXPLAIN statement to analyze query performance?How can you use the EXPLAIN statement to analyze query performance?Apr 28, 2025 am 12:24 AM

The EXPLAIN statement can be used to analyze and improve SQL query performance. 1. Execute the EXPLAIN statement to view the query plan. 2. Analyze the output results, pay attention to access type, index usage and JOIN order. 3. Create or adjust indexes based on the analysis results, optimize JOIN operations, and avoid full table scanning to improve query efficiency.

How do you back up and restore a MySQL database?How do you back up and restore a MySQL database?Apr 28, 2025 am 12:23 AM

Using mysqldump for logical backup and MySQLEnterpriseBackup for hot backup are effective ways to back up MySQL databases. 1. Use mysqldump to back up the database: mysqldump-uroot-pmydatabase>mydatabase_backup.sql. 2. Use MySQLEnterpriseBackup for hot backup: mysqlbackup--user=root-password=password--backup-dir=/path/to/backupbackup. When recovering, use the corresponding life

What are some common causes of slow queries in MySQL?What are some common causes of slow queries in MySQL?Apr 28, 2025 am 12:18 AM

The main reasons for slow MySQL query include missing or improper use of indexes, query complexity, excessive data volume and insufficient hardware resources. Optimization suggestions include: 1. Create appropriate indexes; 2. Optimize query statements; 3. Use table partitioning technology; 4. Appropriately upgrade hardware.

What are views in MySQL?What are views in MySQL?Apr 28, 2025 am 12:04 AM

MySQL view is a virtual table based on SQL query results and does not store data. 1) Views simplify complex queries, 2) Enhance data security, and 3) Maintain data consistency. Views are stored queries in databases that can be used like tables, but data is generated dynamically.

What are the differences in syntax between MySQL and other SQL dialects?What are the differences in syntax between MySQL and other SQL dialects?Apr 27, 2025 am 12:26 AM

MySQLdiffersfromotherSQLdialectsinsyntaxforLIMIT,auto-increment,stringcomparison,subqueries,andperformanceanalysis.1)MySQLusesLIMIT,whileSQLServerusesTOPandOracleusesROWNUM.2)MySQL'sAUTO_INCREMENTcontrastswithPostgreSQL'sSERIALandOracle'ssequenceandt

What is MySQL partitioning?What is MySQL partitioning?Apr 27, 2025 am 12:23 AM

MySQL partitioning improves performance and simplifies maintenance. 1) Divide large tables into small pieces by specific criteria (such as date ranges), 2) physically divide data into independent files, 3) MySQL can focus on related partitions when querying, 4) Query optimizer can skip unrelated partitions, 5) Choosing the right partition strategy and maintaining it regularly is key.

See all articles

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

Video Face Swap

Video Face Swap

Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Tools

EditPlus Chinese cracked version

EditPlus Chinese cracked version

Small size, syntax highlighting, does not support code prompt function

SublimeText3 English version

SublimeText3 English version

Recommended: Win version, supports code prompts!

Dreamweaver Mac version

Dreamweaver Mac version

Visual web development tools

WebStorm Mac version

WebStorm Mac version

Useful JavaScript development tools

SecLists

SecLists

SecLists is the ultimate security tester's companion. It is a collection of various types of lists that are frequently used during security assessments, all in one place. SecLists helps make security testing more efficient and productive by conveniently providing all the lists a security tester might need. List types include usernames, passwords, URLs, fuzzing payloads, sensitive data patterns, web shells, and more. The tester can simply pull this repository onto a new test machine and he will have access to every type of list he needs.