Q&A for professional and enthusiast programmers
(select count(distinct owneruserid) from posts
where creationdate >= '2018-01-01'
and creationdate < '2019-01-01' and posttypeid = 1 and owneruserid is not null) from users where year(users.creationdate) < 2019;
from users where id not in (select owneruserid from posts
where year(creationdate) = 2018 and posttypeid = 1 and
owneruserid is not null) and year(creationdate) < 2019;*/