MYSQL實作排名函數RANK，DENSE_RANK和ROW_NUMBER

1. 并列跳躍排名

select
       score,
       (
           select count(score) + 1 from score s2 
           where s2.score > s.score
       ) ranking
from score s order by score desc;           

1. 并列連續排名

select
       score,
       (
           select count(distinct score) from score s2
           where s2.score >= s.score
       ) ranking
from score s order by score desc;           

1. 分組并列跳躍

select
       score,
       course_id,
       (
           select count(score) + 1 from score s2
           where s2.course_id = s.course_id and s2.score > s.score
        ) ranking
from score s
order by course_id,score desc;           

1. 分組并列連續

select
       score,
       course_id,
       (
           select count(distinct score) from score s2
           where s2.course_id = s.course_id and s2.score >= s.score
        ) ranking
from score s
order by course_id,score desc;