为什么mysqli给出“命令不同步"?错误? [英] Why is mysqli giving a "Commands out of sync" error?

问题描述

我正在尝试运行以下内容.

I am trying to run the following.

<?php

$db = mysqli_connect("localhost","user","pw") or die("Database error");
mysqli_select_db($db, "database");

$agtid = $_POST['level'];

$sql = sprintf("call agent_hier(%d)", $agtid);

$result = mysqli_query($db, $sql) or exit(mysqli_error($db));

if ($result) {
    echo "<table border='1'>
        <tr><th>id</th>
        <th>name</th>
        <th>parent_id</th>
        <th>parent_name</th>
        <th>level</th>
        <th>email</th></tr>";

    while ($row = mysqli_fetch_assoc($result)) 
    {
        $aid = $row["id"];
        $sql2 = "SELECT * FROM members WHERE MEMNO = '$aid'";
        $result2 = mysqli_query($db,$sql2) or exit(mysqli_error($db));

            while ($newArray = mysqli_fetch_array($result2)) {
                $fname = $newArray['FNAME'];
                $lname = $newArray['LNAME'];
                $mi = $newArray['MI'];  
                $address = $newArray['ADDRESS'];    
                $city = $newArray['CITY'];  
                $state = $newArray['STATE'];    
                $zip = $newArray['ZIP'];
                            $kdate = $newArray['KDATE'];
                $date = abs(strtotime(date('m/d/Y')) - strtotime(date($kdate))) / (60 * 60 * 24);
            }

        echo sprintf("<tr><td>%s</td><td>%s</td><td>%s</td><td>%s</td><td>%s</td><td>%s</td></tr>",
            $row["id"],$row["name"],
            $row["parent_id"],$row["parent_name"],
            $row["level"],$row["email"]);
    }

    echo "</table>";
}

mysqli_free_result($result);
mysqli_close($db);

?>

如果我删除以下行:

  $aid = $row["agent_id"];

到......

  $date = abs(strtotime(date('m/d/Y')) - strtotime(date($kdate))) / (60 * 60 * 24);
  }

一切正常.如果没有，则会出现以下错误:

everything will work fine. If not, I get the following error:

命令不同步；您不能立即运行此命令

在研究中，我认为这可能是由于同时运行多个MySQLi查询所致，其中使用mysqli_multi_query，但是对于

In researching, I think it could be due to multiple MySQLi queries run at the same time, in which using mysqli_multi_query but for all the samples and general data in the guide does not seem to be applicable.

有什么想法吗?

推荐答案

MySQL客户端不允许您执行新的查询，在该查询中仍需要从正在进行的查询中获取行.请参见命令不同步有关常见错误的MySQL文档.

The MySQL client does not allow you to execute a new query where there are still rows to be fetched from an in-progress query. See Commands out of sync in the MySQL doc on common errors.

您可以使用 mysqli_store_result() 从外部查询中预提取所有行.这会将它们缓冲在MySQL客户端中，因此从服务器的角度来看，您的应用已获取了完整的结果集.然后，即使在从现在缓冲的外部结果集中提取行的循环中，您也可以执行更多查询.

You can use mysqli_store_result() to pre-fetch all the rows from the outer query. That will buffer them in the MySQL client, so from the server's point of view your app has fetched the full result set. Then you can execute more queries even in a loop of fetching rows from the now-buffered outer result set.

或者您 mysqli_result::fetch_all() 会返回完整的结果集作为一个PHP数组，然后可以在该数组上循环.

Or you mysqli_result::fetch_all() which returns the full result set as a PHP array, and then you can loop over that array.

调用存储过程是一种特殊情况，因为存储过程有可能返回多个结果集，每个结果集可能都有自己的行集.这就是为什么@ a1ex07的答案提到使用mysqli_multi_query()并循环直到mysqli_next_result()没有更多结果集的原因.即使您的存储过程只有一个结果集，这也是满足MySQL协议所必需的.

Calling stored procedures is a special case, because a stored procedure has the potential for returning multiple result sets, each of which may have its own set of rows. That's why the answer from @a1ex07 mentions using mysqli_multi_query() and looping until mysqli_next_result() has no more result sets. This is necessary to satisfy the MySQL protocol, even if in your case your stored procedure has a single result set.

PS:顺便说一句，我看到您正在执行嵌套查询，因为您有代表层次结构的数据.您可能要考虑以不同的方式存储数据，以便可以更轻松地查询它.我对此做了一个名为用于SQL和PHP的分层数据模型的演示 .我还将在我的书中的一章中涉及该主题: SQL反模式:避免数据库编程的陷阱.

PS: By the way, I see you are doing the nested queries because you have data representing a hierarchy. You might want to consider storing the data differently, so you can query it more easily. I did a presentation about this titled Models for Hierarchical Data with SQL and PHP. I also cover this topic in a chapter of my book SQL Antipatterns: Avoiding the Pitfalls of Database Programming.

以下是在CodeIgnitor 3.0.3中实现mysqli_next_result()的方法:

Here is how to implement mysqli_next_result() in CodeIgnitor 3.0.3:

system/database/drivers/mysqli/mysqli_driver.php更改的第262行

protected function _execute($sql)
{
    return $this->conn_id->query($this->_prep_query($sql));
}

对此

protected function _execute($sql)
{
    $results = $this->conn_id->query($this->_prep_query($sql));
    @mysqli_next_result($this->conn_id); // Fix 'command out of sync' error
    return $results;
}

从2.x版本开始，这一直是一个问题.我刚刚更新到3.x，不得不将该hack复制到新版本中.

This has been an issue since 2.x. I just updated to 3.x and had to copy this hack over to the new version.

这篇关于为什么mysqli给出“命令不同步"?错误?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！