帮忙查一下sql语句中的错误

$num=explode(' ',$_POST['name']);

//根据多个关键字构建动态SQL语句
$sql="select * from (";
for($i=0;$i<count($num);$i++){
if($i==0)
$sql.="select * from p_newsbase left join p_newscontent on p_newsbase.id=p_newscontent.nid where title like '%$num[0]%' or author like '%$num[0]%' or p_newsbase.keyword like '%$num[0]%' or content like '%$num[0]%'";
  else
  $sql.=" union select * from p_newsbase left join p_newscontent on p_newsbase.id=p_newscontent.nid where title like '%$num[$i]%' or author like '%$num[$i]%' or p_newsbase.keyword like '%$num[$i]%' or content like '%$num[$i]%'";
}
$sql.=")order by date_time DESC";

作者: chanya   发布时间: 2011-05-31

$sql.=" union select * from p_newsbase left join p_newscontent on p_newsbase.id=p_newscontent.nid where title like '%{$num[$i]}%' or author like '%{$num[$i]}%' or p_newsbase.keyword like '%{$num[$i]}%' or content like '%{$num[$i]}%'";

作者: xuzuning   发布时间: 2011-05-31