{dede:sql}标签中，取出字段后，对字段进行逻辑操作时的嵌套方法

<div>{dede:sql sql='select body from dede_addonarticle where typeid=4  order by rand() LIMIT 1'}
            [field:body runphp='yes']
                $pattern='/key=(.*?)"/';
                $arr = preg_match($pattern, @me,$mc);
                $str = $mc[1];
                @me = '<iframe width="700" height="400" src="'.$str.'" frameborder="0" border="0" marginwidth="0" marginheight="0" scrolling="no" 
　　　　　　　　　　allowfullscreen="true" webkitallowfullscreen="true" mozallowfullscreen="true"></iframe>';
            [/field:body]
          {/dede:sql}</div>