Question

I have a table with the following structure…

--------------------------------
id | state_abbr | poll_date
1       GA         2010-01-01
2       GA         2011-01-01
3       NC         2011-02-01
-------------------------------

I need a query that will bring back the latest poll_date for each state. I am using group by but I can’t find out how to order within that to bring back the latest poll_date. It just brings back the first poll_date for each state. So GA would be 2010-01-01 and the NC would be 2011-02-01 and the order by would then order on those values. What can I do to get around this??

Answer 1

How about

SELECT id, state_abr, poll_date FROM <yourTableName> t INNER JOIN (SELECT MAX(poll_date) max_date, id, state_abbr FROM <yourTableName> GROUP BY state_abr) p ON t.state_abbr = p.state_abbr && t.poll_date = p.max_date;

Since you can’t group on more than 1 thing, this way you perform the group, collect the aggregate max date and then use that data to select the final corresponding row(s).

Edit: removed DISTINCT ROW brain lapse, sorry, its what i get for being up so late. 🙂