In mysql, the effect of dense_rank () is realized. -Do not use dense_rank () to achieve the effect of number sequence.

      This is what I felt when doing the 178. score ranking of the database of leetcode. For details, see: https://blog.csdn.net/weixin_42845682/article/details/105252542
      
      

1. The role of dense_rank ()

      The role of dense_rank is: to sort. And when there are duplicate values, it does not affect the ranking.
      For example, the table is named score and the columns are id and score:

id score
1 	80
2 	90
3 	80 
4 	40

      When using score_rank () to sort scores, the following effects are obtained:

90	1
80	2
80	2
40	3

      This method is very useful, but not in mysql ...

Second, how to achieve the effect of dense_rank () in Mysql

      as follows:

select
	s1.score Score,
	(select 
		count(distinct(s2.score))
	from scores s2 
	where s2.score >= s1.score 
	) as Rank  
from scores s1
order by Rank