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Question
Formatted question description: https://leetcode.ca/all/178.html
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 | +-------+------+
Algorithm
For each score, find out how many different scores are greater than or equal to the score in the table, and then sort them in descending order.
Or, Join (is the short form of Inner Join), the condition is that the score of the right table is greater than or equal to the left table, and then the groups are ranked in descending order of the scores.
Code
SQL
SELECT Score,
(SELECT COUNT(DISTINCT Score) FROM Scores WHERE Score >= s.Score) AS Rank
FROM Scores s ORDER BY Score DESC;
--
SELECT s.Score, COUNT(DISTINCT t.Score) Rank
FROM Scores s JOIN Scores t ON s.Score <= t.Score
GROUP BY s.Id ORDER BY s.Score DESC;