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我对 PDO mysql 查询有疑问

这是我的简单代码（不是真实情况，只是为了向您展示问题）

$connexion = new PDO(SQL_DSN, SQL_USERNAME, SQL_PASSWORD);
$stmt = $connexion->prepare('SELECT * from missions,platforms WHERE missions_platforms_id = exl_platforms_id AND missions_id = :mission');
$stmt->execute(array(":mission" => '1'));
$ligne = $stmt->fetch(PDO::FETCH_ASSOC);
var_dump($stmt);

$stmt = $connexion->prepare('SELECT * from missions,platforms WHERE missions_platforms_id = exl_platforms_id AND missions_id = :mission');
var_dump($stmt);
$stmt = $connexion->prepare('SELECT * from missions,platforms WHERE missions_platforms_id = exl_platforms_id AND missions_id = :mission');
var_dump($stmt);

和输出：

object(PDOStatement)[2]
 public 'queryString' => string 'SELECT * from missions,platforms WHERE missions_platforms_id = platforms_id AND missions_id = :mission' (length=122)

boolean false

object(PDOStatement)[2]
 public 'queryString' => string 'SELECT * from missions,platforms WHERE missions_platforms_id = platforms_id AND missions_id = :mission' (length=122)

为什么第二个 var_dump 返回 false ？

如果我做更多次相同的模式，它会返回 false 一半的时间......

谢谢

4

1 回答 1

2

在读取结果集后尝试关闭结果集光标，PDOStatement::fetch()例如PDOStatement::closeCursor()：

$connexion = new PDO(SQL_DSN, SQL_USERNAME, SQL_PASSWORD);
$stmt = $connexion->prepare('SELECT * from missions,platforms WHERE missions_platforms_id = exl_platforms_id AND missions_id = :mission');
$stmt->execute(array(":mission" => '1'));
$ligne = $stmt->fetch(PDO::FETCH_ASSOC);
var_dump($stmt);
$stmt->closeCursor();

$stmt = $connexion->prepare('SELECT * from missions,platforms WHERE missions_platforms_id = exl_platforms_id AND missions_id = :mission');
var_dump($stmt);
$stmt = $connexion->prepare('SELECT * from missions,platforms WHERE missions_platforms_id = exl_platforms_id AND missions_id = :mission');
var_dump($stmt);

第一条语句是您实际从中获取结果的唯一语句。

于 2011-07-06T16:12:37.987 回答