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    PDOStatement::fetchColumn

    (PHP 5 >= 5.1.0, PHP 7, PHP 8, PECL pdo >= 0.9.0)

    PDOStatement::fetchColumn — 从结果集中的下一行返回单独的一列

    说明

    public PDOStatement::fetchColumn(int $column = 0): mixed

    从结果集中的下一行返回单独的一列，如果没有了，则返回 false 。

    注意:

    PDOStatement::fetchColumn() 不应该用于检索 boolean 列，因为无法区分 false 值和没有更多行可检索。请改用 PDOStatement::fetch()。

    参数

    column

    你想从行里取回的列的索引数字（以0开始的索引）。如果没有提供值，则 PDOStatement::fetchColumn() 获取第一列。

    返回值

    PDOStatement::fetchColumn() 从结果集中的下一行返回单独的一列，如果没有更多行，则返回 false。

    警告

    如果使用 PDOStatement::fetchColumn() 取回数据，则没有办法返回同一行的另外一列。

    错误／异常

    如果属性 PDO::ATTR_ERRMODE 设置为 PDO::ERRMODE_WARNING，则发出级别为 E_WARNING 的错误。

    如果属性 PDO::ATTR_ERRMODE 设置为 PDO::ERRMODE_EXCEPTION，则抛出 PDOException。

    示例

    示例 #1 返回下一行的第一列

    <?php
    $sth     = $dbh->prepare("SELECT name, colour FROM fruit");
    $sth->execute();

    print     "Fetch the first column from the first row in the result set:\n";
    $result = $sth->fetchColumn();
    print     "name = $result\n";

    print     "Fetch the second column from the second row in the result set:\n";
    $result = $sth->fetchColumn(1);
    print     "colour = $result\n";
    ?>

    以上示例会输出：

    Fetch the first column from the first row in the result set:
name = lemon
Fetch the second column from the second row in the result set:
colour = red

    参见

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    User Contributed Notes 3 notes

    up
    52
    PhoneixSegovia at GOOGLE_MAIL_SERVER dot com
    14 years ago
    fetchColumn return boolean false when a row not is found or don't had more rows.
    up
    11
    seanferd at assmasterdonkeyranch dot com
    17 years ago
    This is an excellent method for returning a column count. For example:

    <?php
    $db     = new PDO('mysql:host=localhost;dbname=pictures','user','password');
    $pics = $db->query('SELECT COUNT(id) FROM pics');
    $this->totalpics = $pics->fetchColumn();
    $db = null;
    ?>
    In my case $pics->fetchColumn() returns 641 because that is how many pictures I have in my db.
    up
    0
    theking2(at)king.ma
    10 months ago
    When migrating from mysqli it is important that while mysqli_result::fetch_column will iterate over subsequent rows  PDOStatement::fetchColumn will NOT!

    <?php
    while ( $row0 = $db->query("SELECT `value` FROM `bool`")->fetchColumn(0) ) {
          var_dump( $row0 );
    }
    ?>

    is an endless loop unless the first column in the first row of the table bool is "0".
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