Question

I am having problems understanding how best to tackle this query.

I have a table called user_files. A user can have many files. I want to get a list of users who have not modified any of their files within the last year. If a user has modified at least one of their files within the last year, then that user should be excluded.

  Table: user_files
  file_id | user_id | date_modified
  ----------------------------------
  1        100       2010-10-01
  2        100       2010-11-13
  3        100       2011-01-01
  4        101       2010-10-01
  5        101       2010-06-13
  6        101       2011-04-12
  7        101       2012-04-01

The expected result would only list user_id 100.

Here is some bad sql I have been playing with. The idea is that I find all users who recently modified their files and then find users who are not included in that list.

    select user_id from users where user_id not in
    (
      select user_id from 
      (
        select user_id, story_id, max(date_modified) from user_files 
        where DATE_FORMAT(date_modified, '%Y-%m-%d') >= DATE_SUB(curdate(), INTERVAL 1 YEAR)
        group by user_id
      )x
    )

Thanks

Answer 1

SELECT DISTINCT(f.user_id)
FROM user_files f
WHERE NOT EXISTS(SELECT 1
                 FROM user_files ff
                 WHERE ff.user_id = f.user_id
                 AND ff.date_modified >= DATE_SUB(curdate(), INTERVAL 1 YEAR))

http://sqlfiddle.com/#!2/64e7f/1

Or,

SELECT user_id
FROM user_files
GROUP BY user_id
HAVING MAX(date_modified) < DATE_SUB(curdate(), INTERVAL 1 YEAR)

http://sqlfiddle.com/#!2/64e7f/4