主要是去重和字符串匹配
distinct可以放在函数里，优先运算；
字符串匹配 LIKE '' ,其中_匹配单个字符，%匹配多个。

SELECT  COUNT( DISTINCT device_id) as did_cnt,count(question_id) as question_cnt
from question_practice_detail
where date like '2021-08-__';