检查PDO是否存在的最佳方法是什么 [英] What is the best way to check if something exists with PDO

问题描述

有人告诉我rowCount不安全，所以我想在这里问这个问题，我有2个示例，并且想知道什么是最安全，最漂亮的方法来检查是否存在?

Some one told me rowCount not safe so I like to ask it here, I have 2 examples and like to know what is the safest and nice way to check if something exists?

$sql = "SELECT count(*) FROM users WHERE username = 'administrator'";
$result = $db->prepare($sql);
$result->execute();
echo $result->fetchColumn() ? 'true' : 'false';

或

$sql = "SELECT username FROM users WHERE username = ?";
$result = $db->prepare($sql);
$result->execute(array('administrator'));
echo $result->rowCount() ? 'true' : 'false';

推荐答案

使用prepare和fetchColumn

SELECT COUNT(*)语句具有与预期相同的谓词 SELECT语句，然后使用 PDOStatement :: fetchColumn() 检索 将返回的行数.

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.

$sql = "SELECT COUNT(*) FROM users WHERE username = ?";// use `COUNT(*)`
$result = $db->prepare($sql);
$result->execute(array('administrator'));
echo $result->fetchColumn() ? 'true' : 'false';

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