README_EN.md

178. Rank Scores

中文文档

Description

Table: Scores

+-------------+---------+
| Column Name | Type    |
+-------------+---------+
| id          | int     |
| score       | decimal |
+-------------+---------+
id is the primary key for this table.
Each row of this table contains the score of a game. Score is a floating point value with two decimal places.

 

Write an SQL query to rank the scores. The ranking should be calculated according to the following rules:

• The scores should be ranked from the highest to the lowest.
• If there is a tie between two scores, both should have the same ranking.
• After a tie, the next ranking number should be the next consecutive integer value. In other words, there should be no holes between ranks.

Return the result table ordered by score in descending order.

The query result format is in the following example.

 

Example 1:

Input: 
Scores table:
+----+-------+
| id | score |
+----+-------+
| 1  | 3.50  |
| 2  | 3.65  |
| 3  | 4.00  |
| 4  | 3.85  |
| 5  | 4.00  |
| 6  | 3.65  |
+----+-------+
Output: 
+-------+------+
| score | rank |
+-------+------+
| 4.00  | 1    |
| 4.00  | 1    |
| 3.85  | 2    |
| 3.65  | 3    |
| 3.65  | 3    |
| 3.50  | 4    |
+-------+------+

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;