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  • YII关联查询

    以customer order两个表为例
    //关联查询控制器中
    $customer = Customer::find()->where('name'=>'zhangsan')->one();
    $orders = $customer->hasmany('orders',['customer_id']=>'id')->asArray()->all();
    $orders = $customer->hasmany(Order::className(),['customer_id']=>'id')->asArray()->all();
    
    //customer模型中(优化)
    public function getOrders(){
      $orders = $this->hasmany('orders',['customer_id']=>'id')->asArray()->all();
    }
    //关联查询控制器中就可以这么写
    $customer = Customer::find()->where('name'=>'zhangsan')->one();
    $orders = $customer->getOrders();
    //甚至可以这么写
    $orders = $customer->orders;
    //当获取未定义的类属性时会触发类的__get()魔术方法效果 YII会自动调用 getOrders()方法,而且会加上->all(),所以定义getOrders()时不能带上all()
    
    
    //Order模型
    public function getCustomer(){
      $this->hasOne(Customer::className,['id'=>'customer_id'])->asArray();
    }
    //关联查询控制器中这么写
    $order = Order::find()->where("id"=>'1')->one();
    $customer = $order->customer;
    
    /*
    注意点
    1.关联查询会被缓存
    所以
    $customer = Customer::find()->where('name'=>'zhangsan')->one();
    unset($customer->orders);//清掉缓存
    $order = $customer->orders;
    2.关联查询的多次查询
    $customers = Customer::find()->all();//select * from customer
    foreach($customers as $customer){
    $order = $customer->orders;//select * from order where customer_id = ...
    }
    //以上代码执行了101次sql查询,可以进行如下优化
    $customers = Customer::find()->with('orders')->all();//select * from customer
    foreach($customers as $customer){
    $order = $customer->orders();//select * from order where customer_id in (...)
    }//变成了2次查询
    
    */
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  • 原文地址:https://www.cnblogs.com/isuben/p/5510070.html
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