Yii2——MYSQL操作

先创建连接对象

$connection = new \yii\db\Connection([
    'dsn' => $dsn,
     'username' => $username,
     'password' => $password,
]);
$connection->open();

//查询返回多行：
$command = $connection->createCommand('SELECT * FROM post');
$posts = $command->queryAll();
//返回单行：
$command = $connection->createCommand('SELECT * FROM post WHERE id=1');
$post = $command->queryOne();
//查询多行单值：
$command = $connection->createCommand('SELECT title FROM post');
$titles = $command->queryColumn();
//查询标量值/计算值：
$command = $connection->createCommand('SELECT COUNT(*) FROM post');
$postCount = $command->queryScalar();

打印出AR模式下的sql语句

$coupon = new Coupon;
$coupon = $coupon->find();
var_dump($coupon->createCommand()->getRawSql());
exit;