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我正在使用此代码,但我不明白如何检查查询是否返回零行.我该怎么检查？

$results = $mysqli->query("SELECT ANNOUNCE_NUMBER,ANNOUNCEMENTS,ANNOUNCE_TYPE,POST_DATE FROM home WHERE ANNOUNCE_NUMBER NOT LIKE $excludewelcome AND ANNOUNCE_NUMBER NOT LIKE $excludenews ORDER BY ANNOUNCE_NUMBER DESC LIMIT $position, $items_per_group");
if ($results) { 
    //output results from database

    while($obj = $results->fetch_object())
    {
        if($obj->ANNOUNCE_TYPE=='NEWSEVENTS')
        {
            $realstring='News and Events';
        }
        else
        {
        $realstring='Welcome Note';
        }

        echo '<li id="item_'.$obj->ANNOUNCE_NUMBER.'"><strong>'.$realstring.'</strong></span>';
        echo '<br \>'; 
        echo '('.$obj->POST_DATE.' ) <span class="page_message">'.$obj->ANNOUNCEMENTS.'</span></li>';
    }

}