Question

3055. Top Percentile Fraud

English Version

题目描述

Table: Fraud

+-------------+---------+
| Column Name | Type  |
+-------------+---------+
| policy_id   | int   |
| state     | varchar |
| fraud_score | int   |
+-------------+---------+
policy_id is column of unique values for this table.
This table contains policy id, state, and fraud score.

The Leetcode Insurance Corp has developed an ML-driven predictive model to detect the likelihood of fraudulent claims. Consequently, they allocate their most seasoned claim adjusters to address the top 5% of claims flagged by this model.

Write a solution to find the top 5 percentile of claims from each state.

Return _the result table ordered by _state_ in ascending order, _fraud_score_ in descending order, and _policy_id_ in ascending order._

The result format is in the following example.

 

Example 1:

Input: 
Fraud table:
+-----------+------------+-------------+
| policy_id | state    | fraud_score | 
+-----------+------------+-------------+
| 1     | California | 0.92    | 
| 2     | California | 0.68    |   
| 3     | California | 0.17    | 
| 4     | New York   | 0.94    | 
| 5     | New York   | 0.81    | 
| 6     | New York   | 0.77    |  
| 7     | Texas    | 0.98    |  
| 8     | Texas    | 0.97    | 
| 9     | Texas    | 0.96    | 
| 10    | Florida  | 0.97    |  
| 11    | Florida  | 0.98    | 
| 12    | Florida  | 0.78    | 
| 13    | Florida  | 0.88    | 
| 14    | Florida  | 0.66    | 
+-----------+------------+-------------+
Output: 
+-----------+------------+-------------+
| policy_id | state    | fraud_score |
+-----------+------------+-------------+
| 1     | California | 0.92    | 
| 11    | Florida  | 0.98    | 
| 4     | New York   | 0.94    | 
| 7     | Texas    | 0.98    |  
+-----------+------------+-------------+
Explanation
- For the state of California, only policy ID 1, with a fraud score of 0.92, falls within the top 5 percentile for this state.
- For the state of Florida, only policy ID 11, with a fraud score of 0.98, falls within the top 5 percentile for this state. 
- For the state of New York, only policy ID 4, with a fraud score of 0.94, falls within the top 5 percentile for this state. 
- For the state of Texas, only policy ID 7, with a fraud score of 0.98, falls within the top 5 percentile for this state. 
Output table is ordered by state in ascending order, fraud score in descending order, and policy ID in ascending order.

解法

方法一：使用窗口函数

我们可以使用 RANK() 窗口函数来计算每个州的欺诈分数的排名，然后筛选出排名为 1 的记录，并且按照题目要求排序。

# Write your MySQL query statement below
WITH
  T AS (
    SELECT
      *,
      RANK() OVER (
        PARTITION BY state
        ORDER BY fraud_score DESC
      ) AS rk
    FROM Fraud
  )
SELECT policy_id, state, fraud_score
FROM T
WHERE rk = 1
ORDER BY 2, 3 DESC, 1;