SQL-2

6、求单日留存及一个月的每日留存（快手）

select first_data as '日期'
       count(distinct l.user_id) as '新增用户数',
       round(
           count(distinct case when datediff(log_date,first_date) = 1 then l.user_id else null end) / 
           count(distinct l.user_id)
           ,
           2
       ) as '次日留存率',
       round(       
           count(distinct case when datediff(log_date,first_date) = 29 then l.user_id else null end) / 
           count(distinct l.user_id)
           ,
           2
       ) as '30日留存率',
from user_log l left join
(
    select user_id,min(log_date) as first_date
    from user_log
    group by user_id
)t on l.user_id = t.user_id
group by dirst_date

7、sql如何进行优化（拼多多）