感謝，並this link from github幫助了我很多了。
+
+## Selecting extra fields
+
+When Active Record instance is populated from query results, its attributes are filled up by corresponding column
+values from received data set.
+
+You are able to fetch additional columns or values from query and store it inside the Active Record.
+For example, assume we have a table named 'room', which contains information about rooms available in the hotel.
+Each room stores information about its geometrical size using fields 'length', 'width', 'height'.
+Imagine we need to retrieve list of all available rooms with their volume in descendant order.
+So you can not calculate volume using PHP, because we need to sort the records by its value, but you also want 'volume'
+to be displayed in the list.
+To achieve the goal, you need to declare an extra field in your 'Room' Active Record class, which will store 'volume' value:
+
+```php
+class Room extends \yii\db\ActiveRecord
+{
+ public $volume;
+
+ // ...
+}
+```
+
+Then you need to compose a query, which calculates volume of the room and performs the sort:
+
+```php
+$rooms = Room::find()
+ ->select([
+ '{{room}}.*', // select all columns
+ '([[length]] * [[width]].* [[height]]) AS volume', // calculate a volume
+ ])
+ ->orderBy('volume DESC') // apply sort
+ ->all();
+
+foreach ($rooms as $room) {
+ echo $room->volume; // contains value calculated by SQL
+}
+```
+
+Ability to select extra fields can be exceptionally useful for aggregation queries.
+Assume you need to display a list of customers with the count of orders they have made.
+First of all, you need to declare a `Customer` class with 'orders' relation and extra field for count storage:
+
+```php
+class Customer extends \yii\db\ActiveRecord
+{
+ public $ordersCount;
+
+ // ...
+
+ public function getOrders()
+ {
+ return $this->hasMany(Order::className(), ['customer_id' => 'id']);
//->from(['your_table_alias'=>Order::className()])
+ }
+}
+```
+
+Then you can compose a query, which joins the orders and calculates their count:
+
+```php
+$customers = Customer::find()
+ ->select([
+ '{{customer}}.*', // select all customer fields
+ 'COUNT({{order}}.id) AS ordersCount' // calculate orders count
+ ])
+ ->joinWith('orders') // ensure table junction
+ ->groupBy('{{customer}}.id') // group the result to ensure aggregation function works
+ ->all();
而在你的搜索模式，你應該這樣做
class Search extends yourModel
{
/**
* @inheritdoc
*/
public function rules()
{
return [
your rules.......
];
}
/**
* @inheritdoc
*/
public function scenarios()
{
// bypass scenarios() implementation in the parent class
return Model::scenarios();
}
/**
* Creates data provider instance with search query applied
*
* @param array $params
*
* @return ActiveDataProvider
*/
public function search($params)
{
$query = Fromto::find()->joinWith('orders')->groupBy('{{customer}}.Id');
$dataProvider = new ActiveDataProvider([
'query' => $query,
]);
$this->load($params);
if (!$this->validate()) {
// uncomment the following line if you do not want to return any records when validation fails
// $query->where('0=1');
return $dataProvider;
}
$query->andFilterWhere([
'Id' => $this->Id,
'{{customer}}.customer_column' => $this->your_column,
]);
return $dataProvider;
}
}
，並考慮
<?= GridView::widget([
'dataProvider' => $dataProvider,
'filterModel' => $searchModel,
'columns' => [
['class' => 'yii\grid\SerialColumn'],
'Id',
[
'attribute'=>'your_column',
'label'=>'your label',
'value'=>function($model){
return $model->orders->order_column;
}
],
.....
['class' => 'yii\grid\ActionColumn'],
],
]); ?>