php+mysql+ajax实现单表多字段多关键词查询的方法

<?php
include_once("../phpFiles/connMysql.php");//包含连接数据库的代码
$queryType=$_POST['queryType'];//目标数据表
$queryKeywords=$_POST['queryKeywords'];  //查询词
$queryKeywords = preg_replace('#\s+#', ' ',$queryKeywords);//将字符串中多个连续空格替换为一个空格
$keywords=explode(" ",$queryKeywords); //查询词按空格分割
//根据不同的数据表生成不同的查询语句
if($queryType=="users")
{
  $sqlsmt="select email,truename,enName,stuid,degree,supervisorname,tel,room from $queryType where "; //查询语句的初始值
  //利用循环 生成对每个关键词的查询语句
  foreach ($keywords as $keyword)
  {
    $sqlsmt.="concat(email,truename,enName,stuid,degree,supervisorname,tel,room) like '%$keyword%' or ";//本句是关键，利用concat函数实现从多个字段查询单个关键词，并用' or '关键词把每个关键词的concat结果合并
  }
  $sqlsmt=substr($sqlsmt,0,strlen($sqlsmt)-3); //去掉查询字符串尾部的' or '
  $sqlsmt.=" order by degree asc, stuid desc"; //追加排序子句
}
else if($queryType=="papers")
{
  $sqlsmt="select authors,title,jorc,vap,level,status from $queryType where ";
  foreach ($keywords as $keyword)
  {
    $sqlsmt.="concat(authors,title,jorc,vap,level,status) like '%$keyword%' or ";
  }
  $sqlsmt=substr($sqlsmt,0,strlen($sqlsmt)-3);
  $sqlsmt.=" order by level desc, vap desc";
}
else if($queryType=="softwares")
{
  $sqlsmt="select authors,title,num,date from $queryType where ";
  foreach ($keywords as $keyword)
  {
    $sqlsmt.="concat(authors,title,num,date) like '%$keyword%' or ";
  }
  $sqlsmt=substr($sqlsmt,0,strlen($sqlsmt)-3);
  $sqlsmt.=" order by date desc";
}
else if($queryType=="patents")
{
  $sqlsmt="select authors,title,acceptDate,acceptNum,authorizeDate,authorizeNum from $queryType where ";
  foreach ($keywords as $keyword)
  {
    $sqlsmt.="concat(authors,title,acceptDate,acceptNum,authorizeDate,authorizeNum) like '%$keyword%' or ";
  }
  $sqlsmt=substr($sqlsmt,0,strlen($sqlsmt)-3);
  $sqlsmt.=" order by acceptDate desc";
}
$myrs=mysql_query($sqlsmt);//执行查询
if(mysql_num_rows($myrs)==0)//如果结果为空 返回'no'
{
  echo(json_encode("no"));
}
else //否则返回json格式的结果
{
  while($row=mysql_fetch_array($myrs))
  {
    $temp[]=$row;
  }
  echo(json_encode($temp));
}
?>