php mysqli 循环中的循环

Question

我有一个 mysql table，它包含 2 列，看起来像这样...

-------------------------------------------
| sku                 | superseded_sku    |
+---------------------+-------------------+
| part1               | part2             |
| part2               | part3             |
| part3               | part4             |
| part5               | part6             |
| part6               | part7             |

table 基本上显示了公司销售的产品在哪些地方被更新的产品所取代。我的任务是重塑 table 使其类似于以下内容...

-------------------------------------------
| sku                 | superseded_sku    |
+---------------------+-------------------+
| part1               | part4             |
| part2               | part4             |
| part3               | part4             |
| part5               | part7             |
| part6               | part7             |

从而消除了在列表中随机播放以找到当前替换的需要。

我写了以下内容，其中有一个基本的失败之处在于，如果产品的更换次数超过了我在代码中允许的次数，那么它看起来就不会那么远了。我曾多次尝试包含一个 while 循环、一个 do {} while 循环和一个 foreach 循环，但到目前为止我都失败了。

这是我的代码

<?php    
    // Error reporting on

    ini_set("display_errors", 1);
    ini_set("error_reporting", E_ALL);

    // variables

    // Page variable
    $P = $_REQUEST["p"];

    // variables for latest BritPart list

    $dbhost = 'localhost';
    $dbuser = 'userame';
    $dbpass = 'password';
    $dbselect = 'superseded';

    $mysqli = new mysqli($dbhost, $dbuser, $dbpass, $dbselect);
    if (mysqli_connect_error()) {
        die('Connect Error (' . mysqli_connect_errno() . ') '
        . mysqli_connect_error());
        }

    // Start throwing data about  
    $compare = "SELECT * FROM mar15 ORDER BY sku";

    echo "<h3 style=\"text-align: center;\">Supersedes Tables</h3>
    <div class=\"output\" style=\"width: 940px;\">
    <table cellspacing=\"0\" class=\"db-table\" style=\"width: 940px; border-radius: 5px 5px 0 0\"><thead><tr>
    <th width=\"398\">sku</th>
    <th width=\"270\">superseded_sku</th>
    <th width=\"270\">supersede_length</th>
    </tr></thead>
    <tbody>";

    if ($result = mysqli_query($mysqli,"$compare")) {
        while($row = mysqli_fetch_array($result)) {

            $sku = $row['sku'];
            $ss1 = $row['superseded_sku'];
            $ssl = "1";

    // ---------------------------------------------------------------
    // I want to loop through this section until it doesn't find a match
    // ---------------------------------------------------------------

            $query1 = "SELECT superseded_sku FROM mar15 WHERE sku = \"$ss1\"";
                if ($result1 = mysqli_query($mysqli,"$query1")) {
                    while($row1 = mysqli_fetch_array($result1)) {
                        $ss2 = $row1['superseded_sku'];
                        if($ss2 != $ss1) {
                            $ssl++;
                            $ss1 = $ss2;
                        }
                    }
                }

    // ---------------------------------------------------------------
    // Instead I've done this as I don't know how to do what I want
    // ---------------------------------------------------------------

            $query1 = "SELECT superseded_sku FROM mar15 WHERE sku = \"$ss1\"";
                if ($result1 = mysqli_query($mysqli,"$query1")) {
                    while($row1 = mysqli_fetch_array($result1)) {
                        $ss2 = $row1['superseded_sku'];
                        if($ss2 != $ss1) {
                            $ssl++;
                            $ss1 = $ss2;
                        }
                    }
                }

            $query1 = "SELECT superseded_sku FROM mar15 WHERE sku = \"$ss1\"";
                if ($result1 = mysqli_query($mysqli,"$query1")) {
                    while($row1 = mysqli_fetch_array($result1)) {
                        $ss2 = $row1['superseded_sku'];
                        if($ss2 != $ss1) {
                            $ssl++;
                            $ss1 = $ss2;
                        }
                    }
                }

            $query1 = "SELECT superseded_sku FROM mar15 WHERE sku = \"$ss1\"";
                if ($result1 = mysqli_query($mysqli,"$query1")) {
                    while($row1 = mysqli_fetch_array($result1)) {
                        $ss2 = $row1['superseded_sku'];
                        if($ss2 != $ss1) {
                            $ssl++;
                            $ss1 = $ss2;
                        }
                    }
                }

            $query1 = "SELECT superseded_sku FROM mar15 WHERE sku = \"$ss1\"";
                if ($result1 = mysqli_query($mysqli,"$query1")) {
                    while($row1 = mysqli_fetch_array($result1)) {
                        $ss2 = $row1['superseded_sku'];
                        if($ss2 != $ss1) {
                            $ssl++;
                            $ss1 = $ss2;
                        }
                    }
                }

            $query1 = "SELECT superseded_sku FROM mar15 WHERE sku = \"$ss1\"";
                if ($result1 = mysqli_query($mysqli,"$query1")) {
                    while($row1 = mysqli_fetch_array($result1)) {
                        $ss2 = $row1['superseded_sku'];
                        if($ss2 != $ss1) {
                            $ssl++;
                            $ss1 = $ss2;
                        }
                    }
                }

            $query1 = "SELECT superseded_sku FROM mar15 WHERE sku = \"$ss1\"";
                if ($result1 = mysqli_query($mysqli,"$query1")) {
                    while($row1 = mysqli_fetch_array($result1)) {
                        $ss2 = $row1['superseded_sku'];
                        if($ss2 != $ss1) {
                            $ssl++;
                            $ss1 = $ss2;
                        }
                    }
                }

            $query1 = "SELECT superseded_sku FROM mar15 WHERE sku = \"$ss1\"";
                if ($result1 = mysqli_query($mysqli,"$query1")) {
                    while($row1 = mysqli_fetch_array($result1)) {
                        $ss2 = $row1['superseded_sku'];
                        if($ss2 != $ss1) {
                            $ssl++;
                            $ss1 = $ss2;
                        }
                    }
                }

            $query1 = "SELECT superseded_sku FROM mar15 WHERE sku = \"$ss1\"";
                if ($result1 = mysqli_query($mysqli,"$query1")) {
                    while($row1 = mysqli_fetch_array($result1)) {
                        $ss2 = $row1['superseded_sku'];
                        if($ss2 != $ss1) {
                            $ssl++;
                            $ss1 = $ss2;
                        }
                    }
                }

            $query1 = "SELECT superseded_sku FROM mar15 WHERE sku = \"$ss1\"";
                if ($result1 = mysqli_query($mysqli,"$query1")) {
                    while($row1 = mysqli_fetch_array($result1)) {
                        $ss2 = $row1['superseded_sku'];
                        if($ss2 != $ss1) {
                            $ssl++;
                            $ss1 = $ss2;
                        }
                    }
                }

            $query1 = "SELECT superseded_sku FROM mar15 WHERE sku = \"$ss1\"";
                if ($result1 = mysqli_query($mysqli,"$query1")) {
                    while($row1 = mysqli_fetch_array($result1)) {
                        $ss2 = $row1['superseded_sku'];
                        if($ss2 != $ss1) {
                            $ssl++;
                            $ss1 = $ss2;
                        }
                    }
                }

            $query1 = "SELECT superseded_sku FROM mar15 WHERE sku = \"$ss1\"";
                if ($result1 = mysqli_query($mysqli,"$query1")) {
                    while($row1 = mysqli_fetch_array($result1)) {
                        $ss2 = $row1['superseded_sku'];
                        if($ss2 != $ss1) {
                            $ssl++;
                            $ss1 = $ss2;
                        }
                    }
                }

            $query1 = "SELECT superseded_sku FROM mar15 WHERE sku = \"$ss1\"";
                if ($result1 = mysqli_query($mysqli,"$query1")) {
                    while($row1 = mysqli_fetch_array($result1)) {
                        $ss2 = $row1['superseded_sku'];
                        if($ss2 != $ss1) {
                            $ssl++;
                            $ss1 = $ss2;
                        }
                    }
                }

    // --------------------------------------------------------------------------------------

        echo "<tr";
            if($ssl > 1) {
                echo " style=\"background: #ff0;\"";
            }
        echo ">
                <td width=\"398\">$sku</td>
                <td width=\"270\">$ss1</td>
                <td width=\"270\">$ssl</td>
                </tr>";
    }
    $result->close();
    }
    echo "</tr></tbody></table><a href=\"#\" class=\"export linkbutton\" style=\"margin: 10px 0 0 0; display: block; text-align: center;\">Export CSV</a></div>";

    mysqli_close($mysqli);

?>

你可以看到我已经评论了我想要一个循环的位置，我不知道如何使一个工作但是，我的乡下人方法有效但我对它们不满意并希望改进我的技能。在任何人问之前，这些都不是我的真实 user/pass。

Answer 1

我没有看到任何更新语句，所以我想这不是问题所在。

我也不知道循环是否是最有效的解决方案，但是如果你要循环，你想循环直到 superseded_sku 列中没有元素也存在于sku 列。

使用嵌套的 select 语句很容易检查，例如：

SELECT superseded_sku
FROM mar15
WHERE superseded_sku IN (
  SELECT DISTINCT sku FROM mar15
)

此查询将为您提供 superseded_sku 列中的所有元素，这些元素在 sku 列中具有对应项/需要替换。

因此，虽然此 sql 语句 returns 多于 0 行，但您需要进行更多替换。

您可以更进一步，将其与您的 UPDATE 语句结合起来，但这应该让您开始。

Answer 2

通常，我不提倡在循环中进行数据库查询；它效率低下，可能会导致数据库服务器负载过大。

也就是说，除非您可以重构您的数据模型，否则我看不到太多替代方案。您拥有的是单个 table 中的 parent/child 关系（"superseded_sku" 引用同一 table 的子记录）。这对您尝试做的事情不利，因为您事先不知道子记录是否有自己的子记录。

假设重构不可行，您想运行查询，检查是否有匹配的记录，更新查询并重复直到没有更多记录。

尝试这样的事情...

// get initial result set (don't forget to escape your variables)
$query = "SELECT superseded_sku FROM mar15 WHERE sku = '" .
        mysqli_real_escape_string($mysqli, $ss1) . "'";
$result = mysqli_query($mysqli, $query);

// loop while we have results
while(mysqli_num_rows($result) > 0) {
    $row = mysqli_fetch_array($result);

    // double check the row is valid
    if (empty($row["superseded_sku"])) {
        break;
    }
    $ss1 = $row["superseded_sku"];

    // run the query again to check for further superseded skus
    $query = "SELECT superseded_sku FROM mar15 WHERE sku = '" .
        mysqli_real_escape_string($mysqli, $ss1) . "'";
    $result = mysqli_query($mysqli, $query);
}

我强烈建议不要将此方法用作长期措施，因为它根本无法很好地扩展。您几乎肯定会遇到服务器资源问题或超时，尤其是当您的产品列表继续增长时。如果这是您计划在未来使用的东西，您将需要考虑重构数据。

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