PDO:数据访问抽象层

PDO:数据访问抽象层

一.作用：通过PDO能够访问其他数据库

二.用法
1.造PDO对象
$dsn = "mysql:dbname=test_123;host=localhost"; //数据源 = 驱动名：数据库名;
$pdo = new PDO($dsn,"root","123");

2.写sql语句
$sql = "select * from info";
$sql = "update info sey name='张三' where code='p005'";

3.执行SQL语句，返回PDOStatement对象
$stm = $pdo->query($sql);
$pdo->exec($sql);//适用于增删改

4.读数据
$arr = $stm->fetch(PDO::FETCH_ASSOC);
var_dump($arr);
$arr = $stm->fetchAll(PDO::FETCH_ASSOC);
var_dump($arr);

5.事务功能
$dsn = "mysql:dbname=test_123;host=localhost"; //数据源 = 驱动名：数据库名;
$pdo = new PDO($dsn,"root","123");
把PDO的错误模式设置为异常模式
$pdo->setAttribute(PDO::ATTR_ERRMODE,PDO::ERRMODE_EXCEPTION);

捕获异常
try
{
    //开启事务功能
    $pdo->beginTransaction();
    
    $sql1 = "insert into nation values('n008','哈哈')";
    $sql2 = "insert into nation values('n009','GG')";
    $sql3 = "insert into nation values('n010','MM')";

    $pdo->exec($sql1);
    $pdo->exec($sql2);
    $pdo->exec($sql3);
    
    //提交执行，提交事务
    $pdo->commit();
}
catch(Exception $e)
{
    //捕获异常并解决异常
    //回滚
    $pdo->rollBack();//相当于还原，还原到没有修改之前
}



二.预处理语句


$dsn  = "mysql:dbname=test_123;host=localhost";
$pdo = new PDO($dsn,"root","123");
预处理语句方法一
$sql = "insert into nation values(?,?)";
将预处理语句发送到服务器等待执行，返回PDOStatement对象
$stm = $pdo->prepare($sql);

写法1：较麻烦
$stm->bindParam(1,$code);
$stm->bindParam(2,$nno);
$code = "n011";
$nno ="环境";

写法2：数组要跟问号相对应
$arr = array("n012","环境");

执行
$stm->execute($arr);


预处理语句方法二（最常用）
$dsn  = "mysql:dbname=test_123;host=localhost";

$pdo = new PDO($dsn,"root","123");

$sql = "insert into nation values(:code,:nno)";

$stm = $pdo->prepare($sql);

$arr = array("code"=>"n013","nno"=>"嘿嘿");

$stm->execute($arr);