Question

1211. Queries Quality and Percentage

中文文档

Description

Table: Queries

+-------------+---------+
| Column Name | Type  |
+-------------+---------+
| query_name  | varchar |
| result    | varchar |
| position  | int   |
| rating    | int   |
+-------------+---------+
This table may have duplicate rows.
This table contains information collected from some queries on a database.
The position column has a value from 1 to 500.
The rating column has a value from 1 to 5. Query with rating less than 3 is a poor query.

 

We define query quality as:

The average of the ratio between query rating and its position.

We also define poor query percentage as:

The percentage of all queries with rating less than 3.

Write a solution to find each query_name, the quality and poor_query_percentage.

Both quality and poor_query_percentage should be rounded to 2 decimal places.

Return the result table in any order.

The result format is in the following example.

 

Example 1:

Input: 
Queries table:
+------------+-------------------+----------+--------+
| query_name | result      | position | rating |
+------------+-------------------+----------+--------+
| Dog    | Golden Retriever  | 1    | 5    |
| Dog    | German Shepherd   | 2    | 5    |
| Dog    | Mule        | 200    | 1    |
| Cat    | Shirazi       | 5    | 2    |
| Cat    | Siamese       | 3    | 3    |
| Cat    | Sphynx      | 7    | 4    |
+------------+-------------------+----------+--------+
Output: 
+------------+---------+-----------------------+
| query_name | quality | poor_query_percentage |
+------------+---------+-----------------------+
| Dog    | 2.50  | 33.33         |
| Cat    | 0.66  | 33.33         |
+------------+---------+-----------------------+
Explanation: 
Dog queries quality is ((5 / 1) + (5 / 2) + (1 / 200)) / 3 = 2.50
Dog queries poor_ query_percentage is (1 / 3) * 100 = 33.33

Cat queries quality equals ((2 / 5) + (3 / 3) + (4 / 7)) / 3 = 0.66
Cat queries poor_ query_percentage is (1 / 3) * 100 = 33.33

Solutions

Solution 1: Grouping and Aggregation

We can group the query results by query_name, and then use the AVG and ROUND functions to calculate quality and poor_query_percentage.

# Write your MySQL query statement below
SELECT
  query_name,
  ROUND(AVG(rating / position), 2) AS quality,
  ROUND(AVG(rating < 3) * 100, 2) AS poor_query_percentage
FROM Queries
GROUP BY 1;