Question

My table structure is as follows:

      mid   | tid  | data
    | 1     | 0    |  data
    | 1     | 1    |  data
    | 1     | 2    |  data
    | 1     | 3    |  data
    | 1     | 4    |  data
    | 2     | 0    |  data
    | 2     | 1    |  data
    | 3     | 0    |  data
    | 3     | 1    |  data
    | 3     | 2    |  data
    | 4     | 0    |  data
              .
              .
              .
    | N     | 0    |  data
    | N     | 1    |  data
    | N     | 2    |  data
              .
              .
    | N     | K    |  data

Each record is identified by 2 indices, a mid and tid. The tid will be unique to each mid. For each mid the tid starts at 0 and counts upwards to K. There can be imminently many tids for a given mid, and there can be infinitely many mids.

What I want to do is select the 3 most recent MIDs and their corresponding most recent tids WHERE the data meets some criteria (say > 1). If only MIDs 1, 2, 3, and 4 met the data requirements I would want it to return (omitting 1 since it is not the 3 most recent but rather the 4th):

    | 2     | 1    |  data
    | 3     | 2    |  data
    | 4     | 0    |  data

I am lost on how to do this, any help would be appreciated. A dual order by LIMIT 3 would return

    | 3     | 1    |  data
    | 3     | 2    |  data
    | 4     | 0    |  data

Answer 1

JOIN against a subquery which gets the MAX(tid) for each mid:

SELECT 
  t.mid,
  t.tid,
  t.data
FROM tbl t JOIN (
  SELECT mid, MAX(tid) AS maxtid FROM tbl GROUP BY mid
) m ON t.mid = m.mid AND t.tid = m.tid
/* WHERE (some condition) */
ORDER BY t.mid DESC
LIMIT 3

Update: Added the ORDER BY & LIMIT clause, which I missed in the OP.