README_EN.md

178. Rank Scores

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Description

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`.

Solutions

MySQL8

Use DENSE_RANK() to solve this problem.

DENSE_RANK() OVER (
    PARTITION BY <expression>[{,<expression>...}]
    ORDER BY <expression> [ASC|DESC], [{,<expression>...}]
)

Solution:

# Write your MySQL query statement below
SELECT Score, DENSE_RANK() OVER (ORDER BY Score DESC) 'Rank'
FROM Scores;

MySQL5

MySQL only provides window function after version 8. In previous versions, variables can be used to achieve similar functions:

SELECT Score,
       CONVERT(rk, SIGNED) `Rank`
FROM (SELECT Score,
             IF(@latest = Score, @rank, @rank := @rank + 1) rk,
             @latest := Score
      FROM Scores,
           (SELECT @rank := 0, @latest := NULL) tmp
      ORDER BY Score DESC) s;