src/NotORM/Result.php
function group($columns, $having = ""){
        $this->__destruct();
        $this->group  = $columns;
        $this->having = $having;
        return $this;
    }
function group($columns, $having = ""){
        $this->__destruct();
        $this->group  = $columns;
        $this->having = $having;
        return $this;
    }
Set group clause, more calls rewrite old values

@param string
@param string

@return NotORM_Result fluent interface