学习KING老师的总结一些笔记供以后复习巩固,先要在数据库创建一张有id,username,password,age字段的student数据表

PDO的预处理流程

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(1) $pdo->exec() //返回受影响的记录条数，不支持select语句

<?php
header('content-type:text/html;charset=utf-8');
try{
    $dsn = 'mysql:host=localhost;dbname=test';
    $username = 'root';
    $password = '199486';
    $pdo = new PDO($dsn,$username,$password);
    //数据库的连接信息
    $sql = "INSERT student(username,password,age)VALUES('deng','88888',44)";
    $res = $pdo->exec($sql);
    //返回受影响记录条数
    var_dump($res);
}catch(PDOException $e){
    echo $e->getMessage();
}
?>

(2) $stmt = $pdo->query($sql); 执行一条SQL语句，返回一个PDOStatement对象

<?php
header('content-type:text/html;charset=utf-8');
try{
    $dsn = 'mysql:host=localhost;dbname=test';
    $username = 'root';
    $password = '199486';
    $pdo = new PDO($dsn,$username,$password);
    $sql = "SELECT username,password,age FROM student";
    $stmt = $pdo->query($sql);
    foreach ($stmt as $row){
        print_r($row);
        echo '<br/>';
    }
}catch(PDOException $e){
    echo $e->getMessage();
}
?>

得到的结果为一个关联加索引的数组
Array
(
[username] => weiwei
[0] => weiwei
[password] => 199486
[1] => 199486
[age] => 22
[2] => 22
)

(3) fetch() //得到结果集中的一条记录
里面可放入几种可选参数来筛选返回的数组类型及是否为对象

• PDO::FETCH_ASSOC 返回关联数组*
• PDO::FETCH_NUM 返回索引数组
• PDO::FETCH_BOTH 两种数组
• PDO::FETCH_OBJ 返回对象
  $stmt = $pdo->prepare($sql); // 准备要执行的SQL语句，返回PDOStatement对象
  $res = $stmt->execute() //执行一条预处理语句

<?php
header('content-type:text/html;charset=utf-8');
try{
    $dsn = 'mysql:host=localhost;dbname=test';
    $username = 'root';
    $password = '199486';
    $pdo = new PDO($dsn,$username,$password);
    $sql = "SELECT * FROM student";
    $stmt = $pdo->prepare($sql);
    $res = $stmt->execute();
    if($res){
        while($row = $stmt->fetch(PDO::FETCH_OBJ)){
            print_r($row);
            echo '<hr/>';
        }
    }
}catch(PDOException $e){
    echo $e->getMessage();
}
?>