题解 | #每月各旬有多少人练题#
每月各旬有多少人练题
https://www.nowcoder.com/practice/48c8bef6528d4d838e9646682e2b395d
select
concat(date_format(event_date,'%Y年%m月'),
case
when day(event_date)<10 then'上旬'
when day(event_date)<20 then'中旬'
else '下旬' end) AS dt_range,
count(distinct device_id) as cnt
FROM question_practice_detail
group by dt_range
order by substr(dt_range,6,2) desc,cnt desc
date_format()
concat()
substr()
case when
使用以上3个函数以case when 语句
