两列的Yii2计算结果差

Question

我找不到与我认为更容易解决的问题相关的解决方案。我有两列数值为INT（5）的列，在第三列中我当然应该获得每一行的差值结果。]

我从此link的加法解决方案中得到提示，但每行返回（无值）。>>

在模型Sistop.php中：

public function getDiff()
{
    $this->diff = 0;

    if (is_numeric($this->qdsistop) && is_numeric($this->qusistop)) {
        $this->diff = $this->qdsistop - $this->qusistop;
    }

    return $this->diff;
}
在SistopSearch.php中
class SistopSearch extends Sistop
{

    public function attributes()
    {
        return array_merge(parent::attributes(), ['diff']);
    }

......

   public function search($params)
    {
        $query = Sistop::find()->select('*, (`qdsistop` - `qusistop`) AS `diff`');
        // add conditions that should always apply here
        $dataProvider = new ActiveDataProvider([
            'query' => $query,
        ]);

        // enable sorting for the related columns
        $dataProvider->sort->attributes['diff'] = [
            'asc' => ['diff' => SORT_ASC],
            'desc' => ['diff' => SORT_DESC],
        ];


.....
        if (is_numeric($this->diff)) {
            $query->having([
                'diff' => $this->diff,
            ]);
        }
结果相同：每行（无值）。
提前感谢。

我找不到与我认为更容易解决的问题相关的解决方案。我有两列的数值为INT（5），在第三列中，我应该得到每个列的差值结果...

Answer 1

与数组输入参数一起使用addSelect：

$query = Sistop::find();
$query->addSelect(['([[qdsistop]] - [[qusistop]]) AS [[diff]]']);

// more examples:
$query->addSelect(['SUM(amount) AS total_annual', 'IF(val > 0, 1, 0) AS is_selected']);
$query->addSelect(['DATE_FORMAT(date_created,'%Y-%m') AS yymm']);
$query->andWhere("[[diff]] >= :limit", [':limit' => 100]);
$query->addGroupBy(['is_selected', 'yymm']);
$query->orderBy(['diff' => SORT_DESC])