题解 | #计算用户8月每天的练题数量#
计算用户8月每天的练题数量
http://www.nowcoder.com/practice/847373e2fe8d47b4a2c294bdb5bda8b6
select case date <= '2021-08-31' and date >= '2021-08-01' when 1 then day(date) end day,count(*) question_cnt from question_practice_detail group by day having day is not null;
//不加having筛选,结果集为什么会多出一行null值统计,想不明白。。。。