Q&A for gamemasters and players of tabletop, paper-and-pencil role-playing games
SELECT 100*NRU.#NRU/#U FROM ( SELECT count(IU.Id) as '#U' FROM ( SELECT Users.Id as 'Id' FROM Users, Posts WHERE Users.Id = Posts.OwnerUserId and Posts.PostTypeId = 1 and Posts.Tags like '%arduino%' GROUP BY Users.Id ) as IU ) as U, ( SELECT count(INRU.Id) as '#NRU' FROM ( SELECT Users.Id as 'Id' FROM Users, Posts WHERE Users.Id = Posts.OwnerUserId and Posts.PostTypeId = 1 and Posts.Tags like '%arduino%' and (year(Users.LastAccessDate)<2013 or month(Users.LastAccessDate)<3) GROUP BY Users.Id ) as INRU ) as NRU