// YII2中通过createCommand来处理数据库

// 查询多条记录
// {{%user}} 表示如果设置了表前缀，YII会自动帮你替换
$data1 = YII::$app->db->createCommand('select * from {{%user}}')->queryAll();


// 查询一条记录
// createCommand的第二个参数可以进行参数绑定
$data2 = YII::$app->db->createCommand('select * from {{%user}} where id=:id',['id' => 2])->queryOne();


// 返回一列(第一列)数据
$data3 = YII::$app->db->createCommand('select name from {{%user}}')->queryColumn();


// 返回一个标量值，常用于统计
$data4 = YII::$app->db->createCommand('select count(*) as cnt from {{%user}}')->queryScalar();

// 绑定参数，防止sql注入问题
// bindValue绑定一个参数
$data5 = YII::$app->db->createCommand('select * from {{%user}} where id=:id')
    ->bindValue(':id',3)
    ->queryOne();

// 绑定多个参数
$data6 = YII::$app->db->createCommand('select * from {{%user}} where id=:id and name=:name')
    ->bindValues([':id' => 5,':name' => 'eee'])
    ->queryOne();

// 绑定参数引用
$id = 7;
$data7 = YII::$app->db->createCommand('select * from {{%user}} where id=:id')
    ->bindParam(':id',$id)
    ->queryOne();

// 执行非查询语句
$data8 = YII::$app->db->createCommand('update {{%user}} set name=:name where id=:id')
    ->bindValues([':name' => 'abcdef',':id' => 8])
    ->execute();

// 当然，我们也可以用更加简便的方法
// insert()插入
$data9 = YII::$app->db->createCommand()->insert('{{%user}}',[
    'name' => 'test','sex' => 1,'age' => 28,])->execute();

// batchInsert()批量插入
$data10 = YII::$app->db->createCommand()->batchInsert('{{%user}}',['name','sex','age'],[
    ['111',1,11],['222',22],])->execute();

// update()更新
$data11 = YII::$app->db->createCommand()->update('{{%user}}',[
    'name' => '1242143214'
],'id=:id',['id' => 10])->execute();

// delete()删除
$data12 = YII::$app->db->createCommand()->delete('{{%user}}',['id' => 11])->execute();


// 执行事务
$trans = YII::$app->db->beginTransaction();

try {
    YII::$app->db->createCommand()->update('{{%user}}',['age' => 12],['id' => 13])->execute();
    YII::$app->db->createCommand()->update('{{%user}}',['age' => 22],['id' => 14])->execute();

    $trans->commit();
} catch (\Exception $e) {
    //如果语句中有一个执行失败，那么就将回滚
    $trans->rollBack();
    throw $e;
}

// 获取表的定义信息
$info = YII::$app->db->getTableSchema('{{%user}}');

<?PHP

namespace app\models;

use yii\db\ActiveRecord;

class MyUser extends ActiveRecord
{
    public static function tableName()
    {
        return '{{%user}}';
    }
}　　

// 查询一条记录
// asArray的作用是以数组形式返回结果
// find()会返回一个ActiveQuery对象，ActiveQuery对象继承自yii\db\Query，所以可以使用Query中的所有查询方法
$data1 = MyUser::find()->where(['id' => 1])->asArray()->one();

// 查询多条记录
$data2 = MyUser::find()->where([])->orderBy('id desc')->asArray()->all();

// 根据主键获取一条记录
$data3 = MyUser::findOne(3);

// 根据主键获取多条记录
$data4 = MyUser::findAll([4,5,6,7]);

// 带条件查询多条记录
$data5 = MyUser::findAll(['sex' => 1]);

// 运行原生sql
$data6 = MyUser::findBysql('select * from {{%user}} where id=:id',[':id' => 8])->asArray()->one();

// 添加数据
// 准备一个新的实例，然后设置对应字段属性，保存
$user = new MyUser();
$user->name = 'test';
$user->sex = 1;
$user->age = 22;
$user->save();

// 修改数据
// 先获取一个对象，然后设置对应字段属性，保存
$upd = MyUser::findOne(10);
$upd->name = 'abcdefg';
$upd->save();

// 修改多条数据
$data7 = MyUser::updateAll(['name' => 'update'],['sex' => 1]);

// 删除一条数据
$del = MyUser::findOne(15);
$del->delete();

// 删除多条数据
$data8 = MyUser::deleteAll(['sex' => 0]);

// 事务操作
$user2 = MyUser::findOne(22);
$user3 = MyUser::findOne(33);
$trans = MyUser::getDb()->beginTransaction();
try {
    $user2->name = '2222';
    $user3->name = '3333';
    //修改数据
    $user2->save();
    $user3->save();

    $trans->commit();
} catch (\Exception $e) {
    $trans->rollBack();
    throw $e;
}