mysql - How to select only last entries based on a especific column value keeping the current table order -

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i have table keeps track of last changes applied students in student catalog. want return data table every minute can sincronize necessary entries java app.

it happens need last event_type entry per id. i've created small art graphically explain want site doesnt let me post because of reputation being low yet. i'll try post link though:

what have                                        +---------------------+------------+------------+  +---------------------+------------+------------+ | event_time          | event_type | student_id |  | event_time          | event_type | student_id | +---------------------+------------+------------+  +---------------------+------------+------------+ | 2015-08-16 11:42:08 |          1 |         37 |  | 2015-08-16 11:44:30 |          1 |         37 | | 2015-08-16 11:42:29 |          1 |         37 |  | 2015-08-16 11:45:47 |          2 |         37 | | 2015-08-16 11:43:51 |          2 |         37 |  | 2015-08-16 12:21:40 |          1 |         44 | | 2015-08-16 11:44:13 |          3 |         37 |  | 2015-08-16 12:21:49 |          3 |         44 | | 2015-08-16 11:44:30 |          1 |         37 |  | 2015-08-16 12:21:55 |          2 |         30 | | 2015-08-16 11:45:47 |          2 |         37 |  | 2015-08-16 12:22:00 |          3 |         37 | | 2015-08-16 12:21:28 |          2 |         44 |  | 2015-08-16 12:27:08 |          2 |         44 | | 2015-08-16 12:21:40 |          1 |         44 |  +---------------------+------------+------------+ | 2015-08-16 12:21:49 |          3 |         44 | | 2015-08-16 12:21:55 |          2 |         30 | | 2015-08-16 12:22:00 |          3 |         37 | | 2015-08-16 12:27:08 |          2 |         44 | +---------------------+------------+------------+

any idea how do that? searched site couldnt find suitable this. help!

e.g.:

select x.*    my_table x    join my_table y       on y.student_id = x.student_id     , y.event_time >= x.event_time   group      x.student_id      , x.event_time  having count(*) <= 3   order      event_time;

or, faster...

select event_time      , event_type      , student_id          ( select x.*             , case when @prev = student_id @i := @i + 1 else @i := 1 end             , @prev := student_id           my_table x             , (select @i:=1,@prev:='') vars          order             student_id             , event_time desc      ) n   <= 3  order      event_time;

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