New users on randomly sampled on dates

SQL

select randdates.date, u.user_id, u.user_name, u.user_registration, r.rev_timestamp, r.rev_id, blocked.is_blocked 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 20) randdates
left join
   huwiki_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') 
 left join
 	huwiki_p.revision_userindex r
    on u.user_id = r.rev_user
    and datediff( STR_TO_DATE(r.rev_timestamp, '%Y%m%d%H%i%s'), STR_TO_DATE(u.user_registration, '%Y%m%d%H%i%s')) < 2
 left join
 	(select REPLACE(log_title,'_',' ') as is_blocked from 
		huwiki_p.logging
     where log_type = 'block' and log_action='block') blocked
    on u.user_name = blocked.is_blocked
)
where rev_timestamp is not null
SQL

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