PDO 和嵌套获取

PDO and nested fetching(PDO 和嵌套获取)
本文介绍了PDO 和嵌套获取的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着跟版网的小编来一起学习吧!

问题描述

限时送ChatGPT账号..

假设我有这样的事情:

$db=new PDO($dsn);

$statement=$db->query('Select * from foo');

while ($result=$statement->fetch())
{
    //do something with $result
}

我如何在 while 循环中放置另一个查询?即使我创建了一个新的 PDOStatement 对象,它似乎也会覆盖最顶层 PDO 语句的游标.我看到的唯一其他解决方案是 a) 一次获取整个外部循环或 b) 打开 2 个不同的数据库连接.这些似乎都不是一个好主意,还有其他解决方案吗?

How would I put another query inside of that while loop? Even if I make a new PDOStatement object, it seems that that overwrites the cursor for the topmost PDO statement. The only other solution I see is to either a) fetch the entire outer loop at once or b) open 2 different connections to the database. Neither of these seem like a good idea, are there any other solutions?

推荐答案

你应该能够在你的 while 循环中执行任何你想要的其他查询,我想说;像这样:

You should be able to do any other query you want inside your while loop, I'd say ; something like this :

$db=new PDO($dsn);

$statement=$db->query('Select * from foo');

while ($result=$statement->fetch())
{
    $statement2 = $db->query('Select * from bar');
    while ($result2=$statement2->fetch()) {
        // use result2
    }
}

你试过了吗?它应该工作...

Did you try that ? It should work...


尽管如此,如果可以(如果您的数据没问题,我的意思是),使用 JOIN 仅执行一个查询可能会提高性能:1 个查询而不是多个查询通常更快.


Still, if you can (if it's OK with your data, I mean), using a JOIN to do only one query might be better for performances : 1 query instead of several is generally faster.

这篇关于PDO 和嵌套获取的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持跟版网!

本站部分内容来源互联网,如果有图片或者内容侵犯了您的权益,请联系我们,我们会在确认后第一时间进行删除!

相关文档推荐

Deadlock exception code for PHP, MySQL PDOException?(PHP、MySQL PDOException 的死锁异常代码?)
PHP PDO MySQL scrollable cursor doesn#39;t work(PHP PDO MySQL 可滚动游标不起作用)
PHP PDO ODBC connection(PHP PDO ODBC 连接)
Using PDO::FETCH_CLASS with Magic Methods(使用 PDO::FETCH_CLASS 和魔术方法)
php pdo get only one value from mysql; value that equals to variable(php pdo 只从 mysql 获取一个值;等于变量的值)
MSSQL PDO could not find driver(MSSQL PDO 找不到驱动程序)