Как влиять на релевантность MySQL fulltext поиска?

SELECT * 
    FROM (
        SELECT *, MATCH `text` AGAINST('database') AS `score`
            FROM `articles`
    ) AS `t`
    WHERE `score` > 0
    ORDER BY `source` != 'auto', `score`

SELECT *
    FROM (
        SELECT *, MATCH `text` AGAINST('database') AS `score`
            FROM `articles`
    ) AS `t`
    WHERE `score` > 0
    ORDER BY `score`+(`source` = 'auto')*0.5 DESC