Leetcode 178 Rank Scores

Write a SQL query to rank scores. If there is a tie between two scores, both should have the same ranking. Note that after a tie, the next ranking number should be the next consecutive integer value. In other words, there should be no “holes” between ranks.

+----+-------+
| Id | Score |
+----+-------+
| 1  | 3.50  |
| 2  | 3.65  |
| 3  | 4.00  |
| 4  | 3.85  |
| 5  | 4.00  |
| 6  | 3.65  |
+----+-------+

For example, given the above Scores table, your query should generate the following report (order by highest score):

+-------+---------+
| score | Rank    |
+-------+---------+
| 4.00  | 1       |
| 4.00  | 1       |
| 3.85  | 2       |
| 3.65  | 3       |
| 3.65  | 3       |
| 3.50  | 4       |
+-------+---------+

Important Note: For MySQL solutions, to escape reserved words used as column names, you can use an apostrophe before and after the keyword. For example Rank.

1 利用count(distinct)

对于任意一个值a, 这个值的排名就等于大于等于a的所有值去重之后的个数.

# Write your MySQL query statement below
select score, (select count(distinct score) from Scores where score >= t1.score) as 'Rank' from Scores as t1 order by score desc;

2 窗口函数

不得不说, 窗口函数是真香

在MySQL里Rank是保留字, 所以要用as 'Rank'而不是 as Rank

# Write your MySQL query statement below
select Score, dense_rank() over(order by Score desc) as 'Rank' from Scores;