重置PDO中的光标位置 [英] Reset cursor position in PDO

问题描述

$data=$stmt->fetchAll(); //Dumping the data shows the result. It is also setting the cursor at the end

while($data=$stmt->fetch())
{
//Does not enters loop
//If fetchAll() removes it work as usual
}

我知道它不需要两次获取数据.但是我的主要问题是如何在PDO中重置光标位置?

解决方案

AFAIK无法使用PDO重置游标位置-这可能与某些数据库的兼容性有关，不支持重置内部游标. /p>

如果要对结果进行两次迭代，请将其提取到数组并在此数组上进行迭代:

<?php 
$results = $stmt->fetchAll();  
foreach($results as $row) {
    // first
}

foreach($results as $row) {
    // second
}

编辑:某些数据库支持可滚动的光标.要使用它，请将PDO::CURSOR_SCROLL标志添加到prepare方法(请参见 PDOFetch文档页面中的示例) .但这只会增加前进或后退的可能性，而不会完全倒带.另外，并非所有数据库都支持该类型的游标(例如，MySQL不支持).

$data=$stmt->fetchAll(); //Dumping the data shows the result. It is also setting the cursor at the end

while($data=$stmt->fetch())
{
//Does not enters loop
//If fetchAll() removes it work as usual
}

I know It dont need to fetch data twice. But my main question is How to reset cursor position in PDO?

解决方案

AFAIK there is no possibility to reset cursor position with PDO - that might something to do with compatibility with some databases, that don't support resetting internal cursors.

If you want to iterate twice over the results, fetch it to the array and iterate over this array:

<?php 
$results = $stmt->fetchAll();  
foreach($results as $row) {
    // first
}

foreach($results as $row) {
    // second
}

Edit Some databases support scrollable cursors. To use that, add PDO::CURSOR_SCROLL flag to prepare method (see examples at PDOFetch documentation page). But that only adds possibility to move forward or backward, not rewind completely. Also, not all databases support that type of cursor (e.g. MySQL doesn't).

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