PHP PDO对mysql的常规操作

平时常用框架自带的类来操作数据库，今天重温php的pdo的相关知识，记录如下。

PHP PDO链接MySql数据库

$db = new PDO('mysql:host=localhost;dbname=test','root','123456');
$db->exec('set names utf-8');

其中，localhost可以改写为ip地址。若为正式环境，建议写线上服务器的内网地址；root为数据库用户名，123456为密码。

假若建表如下

CREATE TABLE `news` (
  `id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `title` varchar(255) NOT NULL,
  `ctime` datetime DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8;

查询

简单查询

$sql = "select * from news order by id desc";
$db->query($sql)->fetchAll(PDO::FETCH_ASSOC);

或用占位符

$sql = "select * from news where id >= ? order by id desc";
$sth = $db->prepare($sql);
$sth->execute([1]);
print_r($sth->fetchAll(PDO::FETCH_ASSOC));

若数据量大，为减轻数据库压力，可以用fetch更换fetchAll。再遍历结果集获取查询后的关联数组。

$sql = "select * from news where id >= ? order by id desc";
$sth = $db->prepare($sql);
$result = [];
while($row = $sth->fetch(PDO::FETCH_ASSOC)){
    $result[] = $row;
}

添加

$sql = "insert into news (title,ctime) values ('title1','2017-09-09 10:01:00')";
$sth = $db->prepare($sql);
$sth->execute();

或用占位符

$sql = "insert into news (title, ctime) values (?,?)";
$sth = $db->prepare($sql);
$sth->execute(['title1','2017-09-09 10:01:00']);

添加多条数据

如果想插入多条数据，不想写很多的? ，同时execute又不支持通过二维数组传参 [ ['title1','2017-09-09 10:01:00'], ['title2','2017-09-09 10:02:00'] ].我们可以采用参数绑定的方法（当然也可以拼接sql等），来添加多条数据。

$sql = 'insert into news (title,ctime) values (:title, :ctime)';
$sth = $db->prepare($sql);
$data = [ 
            ['title'=>'title1', 'ctime'=>'2017-09-09 10:01:00'],
            ['title' => 'title2', 'ctime' =>'2017-09-09 10:02:00']
        ];
try {
     $db->beginTransaction();
     foreach ($data as $item) {
         $sth->bindValue(':title', $item['title']);
         $sth->bindValue(':ctime', $item['ctime']);
         $sth->execute();
     }
    $db->commit();
} catch (PDOException $e) {
    $db->rollBack();
}

修改

$sql = "update news set title = 'news01' where id = 1";
$sth = $db->prepare($sql);
$sth->execute();

或

$sql = "update news set title = 'news01' where id = ?";
$sth = $db->prepare($sql);
$sth->execute([1]);

删除

$sql = "delete from news where id = 2";
$sth = $db->prepare($sql);
$sth->execute();

或

$sql = "delete from news where id = ?";
$sth = $db->prepare($sql);
$sth->execute([1]);