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我正在尝试更新旧的 MySQL PHP 方法调用，但我最终调用了两次相同的 SELECT 调用以达到相同的结果。有一个更好的方法吗？

这是原文：

function updateProbabilities()
{
    // first update the word count of each category
    $rs = $this->con->select("SELECT category_id, SUM(count) AS total FROM nb_wordfreqs WHERE 1 GROUP BY category_id");
    $total_words = 0;
    while (!$rs->EOF()) {
        $total_words += $rs->f('total');
        $rs->moveNext();
    }
    $rs->moveStart();
    if ($total_words == 0) {
        $this->con->execute("UPDATE nb_categories SET word_count=0, probability=0 WHERE 1");
        return true;
    }
    while (!$rs->EOF()) {
        $proba = $rs->f('total')/$total_words;
        $this->con->execute("UPDATE nb_categories SET word_count=".(int)$rs->f('total').",
                                    probability=".$proba."
                                    WHERE category_id = '".$rs->f('category_id')."'");
        $rs->moveNext();
    }
    return true;
}

这是我的版本：

function updateProbabilities() {

    $sql = "SELECT category_id, SUM(count) AS total FROM nb_wordfreqs WHERE 1 GROUP BY category_id";
    $res = mysql_query($sql) or die (mysql_error());

    $total_words = 0;

    while ($row = mysql_fetch_array($res, MYSQL_ASSOC)) {
        $total_words += $row['total'];
    }

    if ($total_words >= 1) {

        $sql = "SELECT category_id, SUM(count) AS total FROM nb_wordfreqs WHERE 1 GROUP BY category_id";
        $res = mysql_query($sql) or die (mysql_error());

        while ($row = mysql_fetch_array($res, MYSQL_ASSOC)) {

            $proba = $row['total']/$total_words;

            $count = (int)$row['total'];

            $sql = "UPDATE nb_categories SET word_count=".$count.",
                    probability=".$proba."
                    WHERE category_id = '".$row['category_id']."'";

            mysql_query($sql) or die (mysql_error());
        }

    }
    else {

        $sql = "UPDATE nb_categories SET word_count=0, probability=0 WHERE 1";
        mysql_query($sql) or die (mysql_error());
    }

    return true;
}

你有什么办法可以避免第二次重复的 SELECT 调用吗？

4

3 回答 3

1

第一次运行查询时，将其添加到 while 循环以存储结果：

$rowarray[] = $row; // added to prevent running it twice

然后第二次出现，替换这个：

$sql = "SELECT category_id, SUM(count) AS total FROM nb_wordfreqs WHERE 1 GROUP BY category_id";
$res = mysql_query($sql) or die (mysql_error());
while ($row = mysql_fetch_array($res, MYSQL_ASSOC)) {

有了这个：

foreach ($rowarray as $row) {

ALSO：远离 mysql_ 函数，因为它们已被弃用，很快就会从 PHP 中删除。更改为 PDO 或 MySQLi。您已经在更新代码，也可以进行更改。

于 2013-02-22T17:12:02.880 回答
1

mysql的等价物$rs->moveStart()是：

mysql_data_seek($res, 0);

PS 如果你要重写一个新的 API，你为什么要使用已弃用的 mysql 扩展？你应该使用mysqli还是PDO？他们有类似的方法来倒回光标。

于 2013-02-22T17:15:27.173 回答
-1

您可以将第一个查询设置为唯一变量，并重新使用该查询的结果。

function updateProbabilities() {

$sql = "SELECT category_id, SUM(count) AS total FROM nb_wordfreqs WHERE 1 GROUP BY category_id";
$res = mysql_query($sql) or die (mysql_error());

$total_words = 0;
$results = array();

while ($row1 = mysql_fetch_array($res, MYSQL_ASSOC)) {
    $total_words += $row1['total'];
    $results[] = $row1;
}

if ($total_words >= 1) {

    foreach ($results as $row2) {

        $proba = $row2['total']/$total_words;

        $count = (int)$row2['total'];

        $sql = "UPDATE nb_categories SET word_count=".$count.",
                probability=".$proba."
                WHERE category_id = '".$row2['category_id']."'";

        mysql_query($sql) or die (mysql_error());
    }

}
else {

    $sql = "UPDATE nb_categories SET word_count=0, probability=0 WHERE 1";
    mysql_query($sql) or die (mysql_error());
}

return true;

}

于 2013-02-22T17:16:14.817 回答