public function addGroupBy(string ...$expression) : self
    {
        $this->groupByClauses = array_merge($this->groupByClauses, $expression);

        return $this;
    }
public function addGroupBy(string ...$expression) : self
    {
        $this->groupByClauses = array_merge($this->groupByClauses, $expression);

        return $this;
    }
public function addGroupBy ( string ... $ expression ) : self { $ this -> groupByClauses = array_merge ( $ this -> groupByClauses , $ expression ) ; return $ this ; }
Adds to a "GROUP BY" clause

@param string[] $expression,... A variable list of expressions of what to group by
@return self For method chaining
Adds to a GROUP BY clause