src/bundles/Database/Query/Select.php
public function group_by( $key ) 
	{
		if ( !is_array( $key ) )
		{
			$key = array( $key );	
		}
		
		foreach( $key as $group_key )
		{
			$this->groups[] = $group_key;
		}
		
		return $this;
	}
public function group_by( $key ) 
	{
		if ( !is_array( $key ) )
		{
			$key = array( $key );	
		}
		
		foreach( $key as $group_key )
		{
			$this->groups[] = $group_key;
		}
		
		return $this;
	}
public function group_by ( $ key ) { if ( ! is_array ( $ key ) ) { $ key = array ( $ key ) ; } foreach ( $ key as $ group_key ) { $ this -> groups [ ] = $ group_key ; } return $ this ; }
Add group by stuff

@param mixed 		$key		By passing an array you can add multiple groups
@return self
Add group by stuff