問題描述
我正在嘗試為 PDO 語句的結果編寫一個迭代器，但我找不到任何倒帶到第一行的方法.我想避免調用 fetchAll 和存儲所有結果數據的開銷.
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語句或查找第一行嗎?
Is there some way of reseting the statement or seeking the first row?
推薦答案
我很確定這與數據庫有關.因此，這是您應該盡量避免的.但是，我認為您可以通過啟用緩沖查詢來實現您想要的.如果這不起作用，您始終可以將結果放入帶有 fetchAll.這兩種解決方案都會對您的應用程序性能產生影響，因此如果結果集很大，請三思.
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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