[Wiki] Sort and filter stats columns in a CGridView

create table book (
    id int unsigned not null auto_increment primary key,
    title varchar(255) not null,
    author varchar(255) not null
) engine=innodb default;
 
create table review (
    id int unsigned not null auto_increment primary key,
    book_id int unsigned not null,
    deleted tinyint(1) not null,
    completed tinyint(1) not null,
    rating int(1) unsigned default null,
    critique varchar(4000) default null,
    key book_id (book_id),
        constraint review_ibfk_1
        foreign key (book_id) references book (id)
        on delete cascade on update cascade
) engine=innodb default;

<?php $this->widget('zii.widgets.grid.CGridView', array(
    'id' => 'book-grid',
    'dataProvider' => $model->search(),
    'filter' => $model,
    'columns' => array(
        'title',
        'author',
        array(
            'name' => 'nPending',
            'filter' => CHtml::activeTextField($model, 'n_pending'),
        ),
        array(
            'name' => 'nCompleted',
            'filter' => CHtml::activeTextField($model, 'n_completed'),
        ),
        array(
            'class' => 'CButtonColumn',
        ),
    ),
)); ?>

<?php
class Book extends CActiveRecord {
    /**#@+
     * Property's name is same as the corresponding computed stat column's alias.
     * @var int
     */
    public $nPending;
    public $nCompleted;
    /**#@-*/
 
    /**#@+
     * Property to hold CGV filter form user input. This must be the model's rules 
     * as 'safe', 'on' => 'search'.
     * @var string
     */
    public $n_pending;
    public $n_completed;
    /**#@-*/
 
    /**
     * We put the actual computation of the stats column into the select property of
     * named scopes.
     * @return array The model's array of named scope definitions.
     */
    public function scopes() {
        return array(
            'byNPending' => array('select' =>
                '(select count(*) from review r
                    where r.book_id = t.id && !r.deleted && !r.completed
                ) as nPending'),
            'byNCompleted' => array('select' =>
                '(select count(*) from review w
                    where w.book_id = t.id && !w.deleted && w.completed
                ) as nCompleted'),
        );
    }
 
    /**
     * This is a handy little method for adding compare conditions into a
     * CDbCriteria instance's having property. These conditions work just like the
     * regular CDbCriteria::compare() but in the SQL having clause instead of its
     * where clause.
     * @param CDbCriteria $criteria The criteria to which the having will be added.
     * @param string $attribute Column alias of the stats column to be compared.
     * @param string $input User input with which to compare the stats column.
     */
    private function _compareHaving(&$criteria, $attribute, $input) {
        if ($this->n_pending !== null) {
            $crit = new CDbCriteria;
            $crit->compare($attribute, $this->$input, true);
            $crit->having = $crit->condition;
            $crit->condition = "";
            $criteria->mergeWith($crit);
        }
    }
 
    /**
     * And the model's search method ends up looking like this. About half of this
     * comes from yiic webapp and the rest is new.
     * @return CActiveDataProvider
     */
    public function search() {
        $criteria = new CDbCriteria;
 
        // The scopes will reset the default select so we add what we need here
        $criteria->select = 't.*';
 
        // We don't need to join to the review table for this example but you would
        // need this if the data provider should deliver data from review.
        // $criteria->with = array('reviews');
 
        // Add the two scopes from above to the criteria
        $criteria->scopes = array('byNPending', 'byNCompleted');
 
        $criteria->compare('title', $this->title, true);
        $criteria->compare('author', $this->author, true);
 
        // Add the comparison of user input to computed stat columns using the
        // method we declared before.
        $this->_compareHaving($criteria, 'nPending', 'n_pending');
        $this->_compareHaving($criteria, 'nCompleted', 'n_completed');
 
        // Sorting is required but we need some custom sorting.
        $sort = new CSort('Campaign');
        $sort->attributes = array(
            // * means all the attributes in the models
            '*',
            // but nPending and nCompleted aren't real attributes so they need
            // mentions. I don't know why an empty array works here but it does.
            'nPending' => array(),
            'nCompleted' => array(),
        );
 
        return new CActiveDataProvider($this, array(
            'criteria' => $criteria,
            'sort' => $sort,
        ));
    }
}
?>