Q&A for user experience researchers and experts
with posts_2010 as (select distinct owneruserid from posts where year(creationdate) = 2010), posts_2015 as (select distinct owneruserid from posts where year(creationdate) = 2015) select distinct u.displayname from users u join posts_2015 p15 on u.id = p15.owneruserid left join posts_2010 p10 on u.id = p10.owneruserid where p10.owneruserid is null;