php – 如果有2个具有相同名称的列,如何选择左连接中的列？ [MyS

发布时间：2020-12-13 21:55:54 所属栏目：PHP教程来源：网络整理

导读：我做了一个LEFT JOIN来从我的数据库中获取2个表的值. 查询是这样的： SELECT *FROM thread LEFT JOIN comments ON thread.id_thread = comments.id_threadWHERE id_type = '1'ORDER BY data DESC,hour DESC 然后我以这种方式输出值： ?while($row = mysqli_f

我做了一个LEFT JOIN来从我的数据库中获取2个表的值.
查询是这样的：

SELECT *
FROM thread
  LEFT JOIN comments ON thread.id_thread = comments.id_thread
WHERE id_type = '1'
ORDER BY data DESC,hour DESC

然后我以这种方式输出值：

<?

while($row = mysqli_fetch_array($query))
{
echo '<div class="col-md-1"></div>';
echo '<div class="col-md-11">';
echo  $row['title'] ."<br><br>".$row['content']."<br><br>";
echo  $row['content_com'];
echo '<div class="col-md-2 pull-right">'. "date: ".$row['data']."<br>"."author: ".'<a href ="/user.php?id='.$row['username'].'">'.$row['username'].'</a>'.'</div>' ."<br><br>";
echo '<form role="form" action="commit.php" method="post"><div class="col-md-offset-1 col-md-9"><input class="form-control" type="text" name="comm"><input type="hidden" name="thread_id" value="'.$row['id_thread'].'"></div></form> <br><br><hr><br>';
echo '</div>';
}

mysqli_close($connect);
?>

然后在commit.php(表单操作)中：

<?php
session_start();

  if(isset($_SESSION['id']))
  {
    $servername = "mysql9.000webhost.com";
    $username = "a5461665_admin";
    $password = "xenovia1";
    $dbname = "a5461665_pap";

    $connect  = mysqli_connect($servername,$username,$password,$dbname);

    $id = (isset($_GET['id'])) ? $_GET['id'] : $_SESSION['id'];

    $ctn = $_POST["comm"];

      $com = mysqli_query($connect,"INSERT INTO comments(content_com,id_thread) values ('".$ctn."','".$_POST['thread_id']."')");

      header("location:javascript://history.go(-1)");


    if (!$connect) {
        die("Connection failed: " . mysqli_connect_error());
    }

}
else
{
  header(" url=index.php");
}


 ?>

我的问题是隐藏的输入框是从表注释传递给表单操作字段id_thread,但我希望它从表线程传递字段id_thread,我该怎么做？

解决方法

SELECT *,thread.id_thread as mycol
FROM 
thread LEFT JOIN comments 
ON thread.id_thread=comments.id_thread 
WHERE thread.id_type = '1' 
ORDER BY data desc,hour desc

使用表指定列名称并使用别名.因此,像以前一样对所有列进行SELECT *,现在将thread.id_thread和别名替换为mycol.现在可以作为mycol使用,而且没有更多的名字冲突.

（编辑：李大同）

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