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

SELECT t.pid, t.cost, to.timestamp, t.rid
FROM test as t
JOIN (
    SELECT rid, max(tempstamp) AS maxtimestamp
    FROM test GROUP BY rid
) AS tmax
    ON t.pid = tmax.pid and t.timestamp = tmax.maxtimestamp