力扣sql简单篇练习(二十四)

1 各赛事的用户注册率

1.1 题目内容

1.1.1 基本题目信息

1.1.2 示例输入输出

a 示例输入

b 示例输出

1.2 示例sql语句

SELECT contest_id,ROUND(count(*)/(SELECT count(user_id) FROM Users)*100,2) percentage
FROM Register
GROUP BY contest_id
ORDER BY percentage desc,contest_id asc

1.3 运行截图

2 每台机器的进程平均运行时间

2.1 题目内容

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

SELECT a3.machine_id,ROUND(AVG(a3.t),3) processing_time
FROM
(
    SELECT a1.machine_id,a2.timestamp-a1.timestamp t
    FROM Activity a1
    INNER JOIN Activity a2
    ON a1.machine_id=a2.machine_id AND a1.process_id=a2.process_id 
    AND a1.activity_type='start' AND a2.activity_type='end'
)a3
GROUP BY a3.machine_id

2.3 运行截图

3 发票中的产品金额

3.1 题目内容

3.1.1 基本题目信息1

3.1.2 基本题目信息2

3.1.3 示例输入输出

3.2 示例sql语句

# 如果有含零的列,代表一般都是left join查询,而不是用inner join
SELECT p.name,IFNULL(i.rest,0) rest,IFNULL(i.paid,0) paid,IFNULL(i.canceled,0) canceled,IFNULL(i.refunded,0) refunded
FROM Product p
LEFT JOIN
(
    SELECT product_id,sum(rest) rest,sum(paid) paid,sum(canceled) canceled,sum(refunded) refunded
    FROM Invoice
    GROUP BY product_id
)i
ON p.product_id=i.product_id
ORDER BY name asc

3.3 运行截图