New users on randomly sampled on dates

SQL

select * from 
(select a.Date 
from (
    select curdate() - INTERVAL (a.a + (10 * b.a) + (100 * c.a)) DAY as Date
    from (select 0 as a union all select 1 union all select 2 union all select 3 union all select 4 union all select 5 union all select 6 union all select 7 union all select 8 union all select 9) as a
    cross join (select 0 as a union all select 1 union all select 2 union all select 3 union all select 4 union all select 5 union all select 6 union all select 7 union all select 8 union all select 9) as b
    cross join (select 0 as a union all select 1 union all select 2 union all select 3 union all select 4 union all select 5 union all select 6 union all select 7 union all select 8 union all select 9) as c
) a
where a.Date between '2017-01-01' and '2018-01-01' 
order by rand()
                 limit 1) randdates
left join
   frwiki_p.user u
    on u.user_registration >= DATE_FORMAT(randdates.date,'%Y%m%d%H%i%s')
      and u.user_registration < DATE_FORMAT(date_add(randdates.date, interval 1 day),'%Y%m%d%H%i%s')
SQL

Checking query status...
