LeetCode MySQL 1211. 查询结果的质量和占比

+-------------+---------+
| Column Name | Type    |
+-------------+---------+
| query_name  | varchar |
| result      | varchar |
| position    | int     |
| rating      | int     |
+-------------+---------+
此表没有主键，并可能有重复的行。
此表包含了一些从数据库中收集的查询信息。
“位置”（position）列的值为 1 到 500 。
“评分”（rating）列的值为 1 到 5 。
评分小于 3 的查询被定义为质量很差的查询。

各查询结果的评分与其位置之间比率的平均值。

评分小于 3 的查询结果占全部查询结果的百分比。

查询结果格式如下所示：

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      |
+------------+-------------------+----------+--------+

Result table:
+------------+---------+-----------------------+
| query_name | quality | poor_query_percentage |
+------------+---------+-----------------------+
| Dog        | 2.50    | 33.33                 |
| Cat        | 0.66    | 33.33                 |
+------------+---------+-----------------------+

Dog 查询结果的质量为 ((5 / 1) + (5 / 2) + (1 / 200)) / 3 = 2.50
Dog 查询结果的劣质查询百分比为 (1 / 3) * 100 = 33.33

Cat 查询结果的质量为 ((2 / 5) + (3 / 3) + (4 / 7)) / 3 = 0.66
Cat 查询结果的劣质查询百分比为 (1 / 3) * 100 = 33.33

# Write your MySQL query statement below
select query_name, 
       round(sum(rating/position)/count(*),2) quality,
       round(sum(if(rating<3, 1, 0))*100/count(*) ,2) poor_query_percentage
from Queries
group by query_name

# Write your MySQL query statement below
select query_name, 
       round(avg(rating/position),2) quality,
       round(sum(if(rating<3, 1, 0))*100/count(*) ,2) poor_query_percentage
from Queries
group by query_name