private function removeColumn(PropertyField $field)
    {
        $source = $this->targetModel()->source();

        $sql = strtr(
            'ALTER TABLE `%table` DROP COLUMN `%key`',
            [
                '%table' => $source->table(),
                '%key'   => $field->ident(),
            ]
        );
        $source->db()->query($sql);

        return $this;
    }