protected function buildScore(array $columns, $searchWordsCount)
	{
		$scores = array();
		foreach($columns as $column)
		{
			if($column['scoreFactor'] != 0 && isset($column['expression']))
			{
				$stringConvertedExpression = $this->convertToString($column['type'], $column['expression']);
				$score = $column['scoreFactor'] . '*('
						. $searchWordsCount . '*LENGTH(IFNULL(' . $stringConvertedExpression . ', \'\'))';
				for($i = 0; $i < $searchWordsCount; $i++)
				{
					$score .= ' - LENGTH(REPLACE(LOWER(IFNULL(' . $stringConvertedExpression . ', \'\')), LOWER(:p' . $i . '), \'\'))';
				}
				$score .= ')';
				$scores[] = $score;
			}
		}
		return '' . implode($scores, '+') . '';
	}