问题描述
我正在尝试为 PDO 语句的结果编写一个迭代器，但我找不到任何倒带到第一行的方法.我想避免调用 fetchAll 和存储所有结果数据的开销.
I'm trying to write an iterator for results from a PDO statement but I can't find any way of rewinding to the first row. I would like to avoid the overhead of calling fetchAll and storing all the result data.
// first loop works fine
foreach($statement as $result) {
// do something with result
}
// but subsequent loops don't
foreach($statement as $result) {
// never called
}
有什么方法可以重置语句或查找第一行吗?
Is there some way of reseting the statement or seeking the first row?
推荐答案
我很确定这与数据库有关.因此，这是您应该尽量避免的.但是，我认为您可以通过启用缓冲查询来实现您想要的.如果这不起作用，您始终可以将结果放入带有 fetchAll.这两种解决方案都会对您的应用程序性能产生影响，因此如果结果集很大，请三思.
I'm pretty sure this is database dependent. Because of that, it is something you should try to avoid. However, I think you can achieve what you want by enabling buffered queries. If that doesn't work, you can always pull the result into an array with fetchAll. Both solutions have implications for your applications performance, so think twice about it, if the resultsets are large.
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