力扣sql简单篇练习(十九)

1 查询结果的质量和占比

1.1 题目内容

1.1.1 基本题目信息

1.1.2 示例输入输出

1.2 示例sql语句

# 用count是不会统计为null的数据的
SELECT query_name,ROUND(AVG(rating/position),2) quality,ROUND(count(IF(rating<3,rating,null))/count(rating)*100,2) poor_query_percentage
FROM Queries
GROUP BY query_name

1.3 运行截图

2 每个帖子的评论数

2.1.1 基本题目信息

2.1.2 示例输入输出

2.2 示例sql语句

# 先找到帖子,然后找到回帖的部分 然后进行拼接即可
# 帖子与回帖均有重复的
SELECT s1.sub_id post_id,IFNULL(count(s2.parent_id),0) number_of_comments 
FROM
(
    SELECT distinct sub_id,parent_id
    FROM Submissions
    WHERE parent_id is null
) s1
LEFT JOIN
(
    SELECT distinct sub_id,parent_id
    FROM Submissions
    WHERE parent_id is not null
) s2
ON s1.sub_id=s2.parent_id
GROUP BY s1.sub_id
ORDER BY post_id asc

2.3 运行截图

3 不同国家的天气类型

3.1 题目内容

3.1.1 基本题目信息

3.1.2 示例输入输出

a 示例输入

b 示例输出

3.2 示例sql语句

SELECT c1.country_name,IF(AVG(c2.weather_state)<=15,'Cold',IF(AVG(c2.weather_state)>=25,'Hot','Warm'))  weather_type
FROM Countries c1            
INNER JOIN
(
    SELECT country_id,weather_state,day
    FROM Weather
    WHERE date_format(day,'%Y-%m')='2019-11'
) c2
ON c1.country_id=c2.country_id
GROUP BY c1.country_id

3.3 运行截图