php 上一篇,下一篇文章实现代码与原理说明

mysql_connect('localhost','root','root') or die(mysql_error());
mysql_select_db('cc');
mysql_query("set names 'gbk'");
$cid =5;//是你当前文章的编号
$sql ="select * from string_find where id>$cid order by id desc limit 0,1"; //上一篇文章
$sql1 ="select * from string_find where id<$cid order by id asc limit 0,1";//下一篇文章

$result = mysql_query( $sql );
if( mysql_num_rows( $result ) )
{
$rs = mysql_fetch_array( $result );
echo "上一篇".$rs[0];
}
else
{
echo "没有了";
}

$result1 = mysql_query( $sql1 );
if( mysql_num_rows( $result1 ) )
{
$rs1 = mysql_fetch_array( $result1 );
echo "下一篇".$rs1[0];
}
else
{
echo "没有了";
}

switch($act) {
case "Up":
$SQL="SELECT * FROM `blog` WHERE `ID`< $id ORDER BY `ID` DESC LIMIT 0,1";
break;
case 'Down':
$SQL="SELECT * FROM `blog` WHERE `ID`> $id ORDER BY `ID` ASC LIMIT 0,1";
break;
default :
$SQL="SELECT * FROM `blog` WHERE `ID`= $id LIMIT 0,1";
break;
}