php - Magento Admin Grid Field Custom filter issue -

i have created magento admin module grid , field having custom filter.

    $this->addcolumn('diff', array(         'header'    =>'diff.',         'align'     =>'left',         'type' => 'number',         'index'     =>'diff',         'filter_condition_callback' => array($this, '_difffilter'),     )); 

collection having group below:

$collection->getselect()->group(array('main_table.order_id'));

custom filter function below:

protected function _difffilter($collection, $column) {     if (!$value = $column->getfilter()->getvalue()) {         return $this;     }     $_filter_data = $column->getfilter()->getvalue();                     if($_filter_data["from"]!=''){         $collection->getselect()->having('round((main_table.base_cost-main_table.base_price)*100/main_table.base_cost) >= ?', $_filter_data["from"]);                }      if($_filter_data["to"]!=''){         $collection->getselect()->having('round((main_table.base_cost-main_table.base_price)*100/main_table.base_cost) <= ?', $_filter_data["to"]);     }      return $this; } 

using function if load admin grid it's throwing below error: sqlstate[42s22]: column not found: 1054 unknown column 'main_table.base_cost' in 'having clause'

but grab select query $collection->getselect() using , run mysql directly then, working fine, throwing error magento.

i did lots of research it's not working @ magento.

having clauses used filter results of grouped query. if want filter columns in table, use where clause:

protected function _difffilter($collection, $column) {     if (!$value = $column->getfilter()->getvalue()) {         return $this;     }     $_filter_data = $column->getfilter()->getvalue();                     if($_filter_data["from"]!=''){         $collection->getselect()->where('round((main_table.base_cost-main_table.base_price)*100/main_table.base_cost) >= ?', $_filter_data["from"]);                }      if($_filter_data["to"]!=''){         $collection->getselect()->where('round((main_table.base_cost-main_table.base_price)*100/main_table.base_cost) <= ?', $_filter_data["to"]);     }      return $this; }