SELECT id, dt
FROM ( SELECT test.*,
              CASE WHEN id <> @prev_id OR dt > @prev_dt + 10
                   THEN 1
                   ELSE 0 END next_grp,
              CASE WHEN id <> @prev_id OR dt > @prev_dt + 10
                   THEN @prev_dt := dt END vdt,
              @prev_id := id vid
       FROM test
       CROSS JOIN ( SELECT @prev_id := MIN(id) - 1, 
                           @prev_dt := MIN(dt) - 11
                    FROM test ) init_vars
       ORDER BY test.id, test.dt ) subquery
WHERE next_grp;