MySQL query, MAX() + GROUP BY

Question

Daft SQL question. I have a table like so (\'pid\' is auto-increment primary col)

CREATE TABLE theTable (
    `pid` INT UNSIGNED PRIMARY KEY AUTO_INCREMENT,
          


        

Answer 1

(Tested in PostgreSQL 9.something)

Identify the rid and timestamp.

select rid, max(timestamp) as ts
from test
group by rid;

1   2011-04-14 18:46:00
2   2011-04-14 14:59:00

Join to it.

select test.pid, test.cost, test.timestamp, test.rid
from test
inner join 
    (select rid, max(timestamp) as ts
    from test
    group by rid) maxt
on (test.rid = maxt.rid and test.timestamp = maxt.ts)