我实际上试图使用以下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'";
但发生以下错误：
致命错误：带有消息的未捕获异常'PDOException' 'SQLSTATE [21000]：基数违规：1222使用的SELECT 语句中的列数不同 /opt/lampp/htdocs/project-chg/example.php:21堆栈跟踪：＃0
/opt/lampp/htdocs/project-chg/example.php(21）：PDOStatement-＆gt; execute（）
在第21行的/opt/lampp/htdocs/project-chg/example.php中抛出＃1 {main}
那么我应该怎么做才能纠正这个错误以及如何在适当的帖子上显示评论？ [编辑]： 感谢指出差异@Jakar现在我在研究网络上的其他资源后面临一个新问题，我做了一个加入，结果即将到来但现在的问题是结果似乎是打印所有帖子。而不是他们应该附加的帖子。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;
}
}
答案 0 :(得分：1)
当您使用UNION时，它会组合结果集，为此，每个列的列数必须相同。因此，您不应该SELECT *，而应SELECT col1,col2,col3或列名称。 （无论如何使用SELECT *是不好的做法，因为它会降低代码的可读性，并使PHP与数据库架构更紧密地结合在一起。）
我不知道你的桌面结构是什么样的，所以很难给出一个完美的答案，但我建议你运行两个查询：
$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，如果你确实需要（或更喜欢）UNION，那么就像：
SELECT name,content,id FROM updates...
UNION
SELECT name,content,id FROM comment_update...
因为这样，两个选择都有相同数量的列。
此外，与LIKE列进行比较时，最好使用=而不是char/varchar。