一张表的两个字段对应同一个表的一个字段

问题：a表的两个字段都对应b表的id，如何查询？
解决：将b表当两次用
方法：
select a.id, b.username as answer, c.username as owner  from forum_like as a, users as b, users as c  where a.answer_id=b.id and a.owner_id=c.id;