dropout histogram

SQL

use kowiki_p;

select count(distinct A.rev_user_text)
from 
	
    (select rev_user_text, rev_timestamp
    	from revision
        where
    		(rev_timestamp < timestamp('2017-01-01') and rev_timestamp >= timestamp('2016-12-01'))
    	group by rev_user_text) as A
    
    join
    (select user_name
    from user) as B
    on A.rev_user_text = B.user_name
        
    left join
    (select rev_user_text, rev_timestamp
    	from revision
        where
    		(rev_timestamp < timestamp('2017-03-01') and rev_timestamp >= timestamp('2017-01-01'))
    	group by rev_user_text) as C
    on A.rev_user_text = C.rev_user_text
    
    where (C.rev_user_text is null)
    limit 4000;
SQL

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