1、SQL语句中的limit用法
用法:SELECT * FROM table …… limit 开始位置 , 操作条数
SELECT * FROM table …… limit 0 , 20
从1到20条
SELECT * FROM table …… limit 10 , 20
从11开始取20条值
会从开始位置的后以为开始取.如果要从第五条开始取.开始位置就是4
2、学习分页的一种公式
1.分页原理
所谓分页显示,也就是讲数据库中的结果集,一段一段显示出来
(2)需要的条件
怎么分段,当前在第几段 (每页有几条,当前再第几页)
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
(3)得到公式
Select * from table limit ($Page- 1) * $PageSize, $PageSize
$page代表当前页数.如果是第一页.每页显示10条.那么$page的值为1-1=0.再乘以条数0.就是从0到第10条.如果是第二页.就是2-1=2.再乘以10.就是取第11-20条
3、parse_url()解析URL函数
以数组方式拆解一个url.再取里面的值来使用
- <?PHP
- $ua=parse_url("http://username:password@hostname/path?arg=value#anchor");
- print_r($ua);
- 结果:
-
- Array
- (
- [scheme] => http
- [host] => hostname
- [user] => username
- [pass] => password
- [path] => /path
- [query] => arg=value
- [fragment] => anchor
- )
-
- ?>
4、$_SERVER["REQUEST_URI"]
request_url函数的作用为取得当前URL除域名外的路径
例
当前页为 www.baidu.com/php?id=1
echo $_SERVER["REQUEST_URI"];
结果为php?id=1
完整代码
- <?php
-
-
- include("conn.php");
-
- $pagesize=5;
- $url=$_SERVER["REQUEST_URI"];
- $url=parse_url($url);
- $url=$url[path];
-
-
- $numq=mysql_query("SELECT * FROM `test`");
- $num = mysql_num_rows($numq);
-
- if($_GET[page]){
- $pageval=$_GET[page];
- $page=($pageval-1)*$pagesize;
- $page.=',';
- }
-
- if($num > $pagesize){
- if($pageval<=1)$pageval=1;
- echo "共 $num 条".
- " <a href=$url?page=".($pageval-1).">上一页</a> <a href=$url?page=".($pageval+1).">下一页</a>";
- }
-
-
- $SQL="SELECT * FROM `test` limit $page $pagesize ";
- $query=mysql_query($SQL);
- while($row=mysql_fetch_array($query)){
-
- echo "<hr><b>".$row[name]." | ".$row[sex];
-
- }
- ?>
较完美代码
- <?php
-
- function _PAGEFT($totle, $displaypg = 20, $url = '') {
-
- global $page, $firstcount, $pagenav, $_SERVER;
-
- $GLOBALS["displaypg"] = $displaypg;
-
- if (!$page)
- $page = 1;
- if (!$url) {
- $url = $_SERVER["REQUEST_URI"];
- }
-
-
- $parse_url = parse_url($url);
- $url_query = $parse_url["query"];
- if ($url_query) {
- $url_query = ereg_replace("(^|&)page=$page", "", $url_query);
- $url = str_replace($parse_url["query"], $url_query, $url);
- if ($url_query)
- $url .= "&page";
- else
- $url .= "page";
- } else {
- $url .= "?page";
- }
- $lastpg = ceil($totle / $displaypg);
- $page = min($lastpg, $page);
- $prepg = $page -1;
- $nextpg = ($page == $lastpg ? 0 : $page +1);
- $firstcount = ($page -1) * $displaypg;
-
-
- $pagenav = "显示第 <B>" . ($totle ? ($firstcount +1) : 0) . "</B>-<B>" . min($firstcount + $displaypg, $totle) . "</B> 条记录,共 $totle 条记录";
-
-
- if ($lastpg <= 1)
- return false;
-
- $pagenav .= " <a href='$url=1'>首页</a> ";
- if ($prepg)
- $pagenav .= " <a href='$url=$prepg'>前页</a> ";
- else
- $pagenav .= " 前页 ";
- if ($nextpg)
- $pagenav .= " <a href='$url=$nextpg'>后页</a> ";
- else
- $pagenav .= " 后页 ";
- $pagenav .= " <a href='$url=$lastpg'>尾页</a> ";
-
-
- $pagenav .= " 到第 <select name='topage' size='1' onchange='window.location=\"$url=\"+this.value'>\n";
- for ($i = 1; $i <= $lastpg; $i++) {
- if ($i == $page)
- $pagenav .= "<option value='$i' selected>$i</option>\n";
- else
- $pagenav .= "<option value='$i'>$i</option>\n";
- }
- $pagenav .= "</select> 页,共 $lastpg 页";
- }
-
-
- include("conn.php");
-
- $result=mysql_query("SELECT * FROM `test`");
- $total=mysql_num_rows($result);
-
- _PAGEFT($total,5);
- echo $pagenav;
-
- $result=mysql_query("SELECT * FROM `test` limit $firstcount,$displaypg ");
- while($row=mysql_fetch_array($result)){
-
- echo "<hr><b>".$row[name]." | ".$row[sex];
-
- }
-
-
- ?>