【牛客】SQL127 月总刷题数和日均刷题数

talle20212024-03-02 5:09

描述

现有一张题目练习记录表practice_record，示例内容如下：

|----|------|-------------|---------------------|-------|
| id | uid | question_id | submit_time | score |
| 1 | 1001 | 8001 | 2021-08-02 11:41:01 | 60 |
| 2 | 1002 | 8001 | 2021-09-02 19:30:01 | 50 |
| 3 | 1002 | 8001 | 2021-09-02 19:20:01 | 70 |
| 4 | 1002 | 8002 | 2021-09-02 19:38:01 | 70 |
| 5 | 1003 | 8002 | 2021-08-01 19:38:01 | 80 |

请从中统计出2021年每个月里用户的月总刷题数month_q_cnt 和日均刷题数avg_day_q_cnt（按月份升序排序）以及该年的总体情况，示例数据输出如下：

|--------------|-------------|---------------|
| submit_month | month_q_cnt | avg_day_q_cnt |
| 202108 | 2 | 0.065 |
| 202109 | 3 | 0.100 |
| 2021汇总 | 5 | 0.161 |

解释：2021年8月共有2次刷题记录，日均刷题数为2/31=0.065（保留3位小数）；2021年9月共有3次刷题记录，日均刷题数为3/30=0.100；2021年共有5次刷题记录（年度汇总平均无实际意义，这里我们按照31天来算5/31=0.161）

sql 复制代码

# 获取当月的天数：dayofmonth(last_day(submit_time))

select
date_format (submit_time,'%Y%m') as submit_month,
count(1) as month_q_cnt,
round(count(1)/ max(dayofmonth(last_day(submit_time))),3) as avg_day_q_cnt
from practice_record
where left(submit_time,4)=2021
group by submit_month

union all

select
'2021汇总' as submit_month,
count(1) as month_q_cnt,
round(count(1)/ 31,3)as avg_day_q_cnt
from practice_record
where left(submit_time,4)=2021

order by submit_month