检查数据库表中的某些记录的最快方法是什么?

I have a huge table to work with . I want to check if there are some records whose parent_id equals my passing value . currently what I implement this is by using "select count(*) from mytable where parent_id = :id"; if the result > 0 , means the they do exist.I have a huge table to work with . I want to ch