php - 如何纠正 php mysql 中的基数违规错误消息

Question

我实际上正在尝试使用以下 sql 获取评论系统的值:

$sql="select * from updates where account_name=:either and type IN ('a', 'c') "
      . "  union "
      . "select * from comment_update where os_id=:statusid and type='b'";

但是出现如下错误:

Fatal error: Uncaught exception 'PDOException' with message 'SQLSTATE[21000]: Cardinality violation: 1222 The used SELECT statements have a different number of columns' in
/opt/lampp/htdocs/project-chg/example.php:21 Stack trace: #0
/opt/lampp/htdocs/project-chg/example.php(21): PDOStatement->execute()
#1 {main} thrown in /opt/lampp/htdocs/project-chg/example.php on line 21

那么我应该怎么做才能纠正这个错误以及如何将评论显示到适当的帖子？[编辑]:感谢指出差异 @Jakar 现在我在研究网络上的其他资源后遇到了一个新问题，我做了一个连接并且结果即将到来但现在的问题是结果似乎正在打印所有帖子。而不是应该附在帖子上的帖子。好像我搞砸了循环你能为我指出正确的循环吗？？？这是代码:

 <?php
      $status2view=$project->statusView($_SESSION['uname']);

    foreach($status2view as $row){
           //print_r($row);
           $status_id=$row['update_id'];
        //   SELECT * FROM Product,Color WHERE Product.Name = Color.Name 
        $sql="select update_id,update_body, time, title, author,type from updates where account_name=:either and type IN ('a', 'c') "
                  . "  union "
                  . "select comment_id, author,time,comment_body,os_id ,type from comment_update where os_id=:statusid and type='b'";
        $sql1="select comment_update.comment_id, comment_update.author,comment_update.time,comment_update.comment_body,comment_update.os_id ,comment_update.type from updates,comment_update where comment_update.os_id like updates.update_id ";
        $stmth=$conn->prepare($sql1);
      //  $stmth->bindparam(":either",$_SESSION['uname']);
        //$stmth->bindparam(":statusid",$status_id);
        $stmth->execute();
        $status_reply= $stmth->fetchAll(PDO::FETCH_ASSOC);

        ?>
    </div>    
    <div class="col-lg-8">
        <?php
     foreach ($status_reply as $row1) {


         $status_reply_id=$row1['comment_id'];

                $reply_author=$row1['author'];
                $reply_d=htmlentities($row1['comment_body']);
                $reply_data=  stripslashes($reply_d);
                $reply_osid=$row1['os_id'];

               $reply_date=$row1['time'];
               $reply_delete_button="";
               if ($reply_author==$_SESSION['uname'] || $account_name==$_SESSION['uname']) {
                   $reply_delete_button.="<li><span id='$status_reply_id' class='delete_reply_btn glyphicon glyphicon-remove'><a href='#' title='Delete this comment'>Remove X</a></span></li>";
               }




              $status_replies="<div  class='replyboxes pull-left reply_".$status_reply_id."'><b>Reply by:-<a href='search_results.php?u=".$reply_author."'>".$reply_author."</a>"
                      . "<span class='pull-right'>".$reply_date 
                       . "<b class='caret'>
                         <small><span class='btn-xs btn-danger dropdown-toggle pull-right' data-toggle='dropdown' aria-expanded='true' ><span class='glyphicon glyphicon-edit'></span>
                        <ul class='dropdown-menu'>".$reply_delete_button
                      . "<li><a href='#' class='hidden_text_area glyphicon glyphicon-pencil reply_".$status_reply_id."' title='Edit this comment' >Edit</a></li>"
                      . "<li><a href='report.php?u='".$reply_author."'>Report</a><li></ul>"
                      . "</span></span></small></b><br><legend>".  html_entity_decode($reply_data)."</legend><br></div>";


     }

    foreach($status2view as $row){
         $updateid=$row['update_id'];
                $account_name=$row['account_name'];
                $os_id=$row['os_id'];
                $author=$row['author'];
                $post_date=$row['time'];
                $title= stripslashes($row['title']);
                $data= stripslashes($row['update_body']);

                $statusdeletebutton='';
                //insert_status_ui script to get message.
                if ($author==$_SESSION['uname'] || $account_name==$_SESSION['uname']) {
                $statusdeletebutton='<li>'
                           . '<a href="#" type="'.$updateid.'" class="delete_4_session hidden_text_delete_'.$updateid.' glyphicon glyphicon-trash delete_reply_btn" title="Delete this status and its replies">Remove</a></li>';
                }
                $status_list= $statusui_edit.'<div attr="'.$updateid.'" type="'.$updateid.'" class="statusboxes status_'.$updateid.'  jumbotron">'
                        . '<h3 style="color:black; margin-bottom:5px; margin-top:5px;" class="pull-left">'
                        . '<div id="'.$updateid.'" class="title_s_2copy" value="'.html_entity_decode($title).'">'.html_entity_decode($title).'</div></h3>'
                        . '<span class="pull-right">'
                        . '<div class="dropdown">'
                        . '<button type="button" class="btn btn-danger dropdown-toggle" data-toggle="dropdown"  >'
                        . '<span class="glyphicon glyphicon-edit"></span></button>'
                        . '<ul class="dropdown-menu">'
                        . '<li><a href="#" attr="'.$updateid.'" type="'.$updateid.'" class="edit_4_session hidden_text_edit glyphicon glyphicon-pencil" title="Edit this status" >Edit</a></li>'.$statusdeletebutton.'</ul></div></span><br><hr>'
                        . '<legend><span class=" data_s_2copy" type="'.$updateid.'" >'
                        . html_entity_decode($data).'</span><br><br></legend><b style="text-align:right; color:black;"><small>Posted by:-  <a href="search_results.php?u='.$author.'">'.$author.   '</a>   '.$post_date.'</small></b>'
                        . '<br><p>'.$status_replies.'</p><br>';

                    $status_list.= '<textarea id="reply_textarea_'.$updateid.'"  class="status_reply_'.$updateid.' input-custom2" placeholder="comment\'s"></textarea>'
                            . '<button id="reply_btn_'.$updateid.'" attr="'.$updateid.'" type="b" class="btn btn-warning pull-right btn-sm reply_btn reply_'.$updateid.'">Reply</button></div>';



                echo $status_list;

    }

    }

Answer 1

当您使用 UNION 时，它会合并结果集，为此，每个结果集的列数必须相同。因此，您不应SELECT *，而应SELECT col1,col2,col3 或任何您的列名。 (无论如何，使用 SELECT * 是一种不好的做法，因为它会降低代码的可读性并使 PHP 与数据库模式更紧密地耦合)。

我不知道你的表结构是什么样的，所以很难给出一个完美的答案，但我建议运行两个查询:

$sql =
    "SELECT column_list... FROM updates 
         WHERE account_name LIKE :either AND type IN ('a','c');"
    ."SELECT column_list... FROM comment_update 
          WHERE os_id=:statusid AND type LIKE 'b';"

否则，如果您确实需要(或更喜欢)UNION，那么可以这样:

SELECT name,content,id FROM updates...
UNION
SELECT name,content,id FROM comment_update...

因为这样你在两个选择上有相同数量的列。

此外，在与 char/varchar 列进行比较时，最好使用 LIKE 而不是 =。