在这种情况下如何循环查询？

Question

我一直在尝试循环此查询，但我得到的只是第一个值。

当我在工作台中执行相同的命令时，将获得所有值。 我在这里做错了什么？ 任何答案都非常感谢！

global $db;
$stmt12 = $db->query('SELECT `Value` FROM overriddenpropertyvalues WHERE ParentGUID LIKE "' . $itemguid . '";');
$propertyvaluerow = $stmt12->fetch();
while ($propertyvaluerow != null) {

Answer 1

您仅通过->fetch()获取一个值。 这就是为什么您只获得一个价值的原因。

这里的例子：

$query = $db->prepare('SELECT `Value` FROM `overriddenpropertyvalues` WHERE ParentGUID LIKE :like');

$query->execute([':like' => $itemguid]);

$stmt->bind_result($value);

while ($query->fetch()) {
    echo $value."<br/>"
}

Answer 2

根据$ stmt12-> fetch（）的操作，您的程序中可能存在漏洞。 如果它获取数据数组，则while循环可能无法按预期方式运行。 以下是您可能想尝试的替代方案：

    <?php
        global $db;
        $stmt12         = $db->query('SELECT `Value` FROM overriddenpropertyvalues WHERE ParentGUID LIKE "' . $itemguid . '";');
        // ASSUMES YOU ARE USING PDO SO WE FETCH ALL THE DATA
        $propertyvaluerow = $stmt12->fetchAll();

        // THERE MIGHT BE A LOOPHOLE IN YOUR PROGRAM DEPENDING ON WHAT $stmt12->fetch() IS AND DOES
        // ASSUMING IT FETCHES AN ARRAY OF NESTED OBJECTS OR SCALAR VALUES, THE WHILE LOOP WOULD NOT BEHAVE AS EXPECTED.
        // THAT MEANS IF IT IS AN ARRAY YOU COULD USE A DIFFERENT CONSTRUCT LIKE THE ONE BELOW YOUR WHILE CONSTRUCT:
        /* while ($propertyvaluerow != null) { */

        // CREATE A $count VARIABLE TO HOLD THE INCREMENTAL COUNT THROUGH THE ITERATION:
        $count  = count($propertyvaluerow);

        while($count > 0){
            // DO YOUR WORK HERE

            //DECREMENT THE VALUE OF COUNT OTHERWISE YOU MAY HAVE AN INFINITE LOOP TO DEAL WITH.
            $count--;
        }

    ?>

还有另一种选择：

   <?php            
        // OR EVEN A MUCH MORE EASIER WAY IS TO USE THE FOREACH LOOP, WHICH ACHIEVES THE SAME THING AS THE WHILE LOOP:
        foreach($propertyvaluerow as $iKey=>$objData){
            // SIMPLY USE THE $objData IN WITHING THE LOOP
            // THE $objData IS THE VALUE OF THE CURRENT OBJECT IN THE $propertyvaluerow IN THE ITERATION
        }   

Answer 3

最好的办法：

global $db;
$stmt = $db->prepare('SELECT `Value` FROM OverriddenPropertyValues WHERE ParentGUID=?');
$stmt->execute([$itemguid]);
$rows = $stmt->fetchAll();

foreach($rows as $row) {
    // $row->Value or $row['Value']
}