使用PDO的行数 [英] Row count with PDO

问题描述

周围有许多矛盾的陈述.在PHP中使用PDO进行行计数的最佳方法是什么?在使用PDO之前，我只是使用mysql_num_rows.

There are many conflicting statements around. What is the best way to row count using PDO in PHP? Before using PDO, I just simply used mysql_num_rows.

fetchAll是我不想要的东西，因为有时我可能要处理大型数据集，所以对我的使用不利.

fetchAll is something I won't want because I may sometimes be dealing with large datasets, so not good for my use.

您有什么建议吗?

推荐答案

$sql = "SELECT count(*) FROM `table` WHERE foo = ?"; 
$result = $con->prepare($sql); 
$result->execute([$bar]); 
$number_of_rows = $result->fetchColumn(); 

这不是最优雅的方式，而且还涉及一个额外的查询.

Not the most elegant way to do it, plus it involves an extra query.

PDO具有PDOStatement::rowCount()，显然在MySql中不起作用.真痛苦.

PDO has PDOStatement::rowCount(), which apparently does not work in MySql. What a pain.

从PDO文档中:

对于大多数数据库， PDOStatement :: rowCount()不 返回受影响的行数 SELECT语句.相反，使用 PDO :: query()发出选择 COUNT(*)条相同的语句 谓词为您想要的SELECT 声明，然后使用 PDOStatement :: fetchColumn()到 检索将要执行的行数 被退回.您的应用程序可以 执行正确的操作.

For most databases, PDOStatement::rowCount() does not return the number of rows affected by a SELECT statement. Instead, use PDO::query() to issue a SELECT COUNT(*) statement with the same predicates as your intended SELECT statement, then use PDOStatement::fetchColumn() to retrieve the number of rows that will be returned. Your application can then perform the correct action.

上面的代码示例使用一个预准备的语句，在许多情况下，出于计数行的目的，这可能是不必要的，因此:

The above code example uses a prepared statement, which is in many cases is probably unnecessary for the purpose of counting rows, so:

$nRows = $pdo->query('select count(*) from blah')->fetchColumn(); 
echo $nRows;

这篇关于使用PDO的行数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IT屋！