Question

如何通过Yii Active Record找到数据库中一列的最大值？

我可以通过纯sql和createCommand方法来实现，但我想通过Active Record和CDbCriteria class来实现它。有没有办法做到这一点？

Answer 1

您需要更改选择条件，如下所示。

$model = new Model;
$criteria=new CDbCriteria;
$criteria->select='max(column) AS maxColumn';
$row = $model->model()->find($criteria);
$somevariable = $row['maxColumn'];

参考：

http://www.yiiframework.com/forum/index.php/topic/6730-how-can-i-use-max-in-find-method/page_view_findpost_p_80659

Answer 2

这可以避免创建不必要的临时对象：

$criteria = new CDbCriteria;
$criteria->select = 'max(column)';
// additional where conditions, if you so wish
$criteria->addColumnCondition(array('published' => 1));
$model = SomeModel::model();
$value = $model->commandBuilder->createFindCommand(
    $model->tableName(), $criteria)->queryScalar();

Answer 3

如果您需要WHERE子句：

在控制器中：

$max = $model->getMax($filter);

模特：

public $maxColumn = 0;
public function getMax($filter = null)
{
    /* Get max in column1 WHERE column2 = $filter */
    $criteria               = new CDbCriteria;
    $criteria->select       = 'MAX(t.column1) as maxColumn';
    $criteria->condition    = 't.column2 LIKE :parm';
    $criteria->params       = array(':parm'=>$filter);

    $tempmodel  = $this->find($criteria);
    $max        = $tempmodel['maxColumn'];
    return $max;
}

Answer 4

您可以通过DESC限制结果和顺序，例如

$criteria = new CDbCriteria;
$criteria->order = 'column DESC';
$row = Model::model()->find($criteria);
$somevariable = $row->column;

Answer 5

$model = MyModel::model();

$maxId = $model->getCommandBuilder()
        ->createSqlCommand('SELECT MAX(id) FROM '.$model->tableName())
        ->queryScalar();

$maxId = Yii::app()->db
        ->createCommand('SELECT MAX(id) FROM '.$model->tableName())
        ->queryScalar();

Answer 6

就是这样。

for(int i = 0; i< myObject.FieldOfArrayBytes; i++)
ms.Write(littlechunk);
// continue while all data are wrote.

使用Yii Active Record查找最多一列

6 个答案: