题解 | #计算用户8月每天的练题数量#

select 
  day(date) as day,
  count(question_id) as question_cnt
from question_practice_detail
where month(date)=8 and year(date)=2021
group by date

限定条件：2021年8月，写法有很多种，比如用year/month函数的year(date)=2021 and month(date)=8，比如用date_format函数的date_format(date, "%Y-%m")="202108"

每天：按天分组group by date

题目数量：count(question_id)

细节问题：表头重命名：as

输出示例中每天的字段只取了几号，要去掉年月，用day函数即可

遇到这种模糊查询，like 关键字特别好用，下面是使用 like 关键字查询的题解：

SELECT DAY(date) day,

COUNT(question_id) question_cnt

FROM question_practice_detail

WHERE date like '%2021-08%'

GROUP BY day;