How to select multiple rows by multi-column primary key in MySQL?

Question

I have a table with a multi-column primary key (city/state/date) and many more columns of data. I\'m looking to get the latest data for each city/state. How do I do that cleanly

Answer 1

MySQL supports tuple comparisons:

SELECT * FROM data WHERE 
 (state, city, date) IN (
  ('CA', 'San Francisco', '2013-09-01'), 
  ('CA', 'Los Angeles', '2013-08-01'), 
  ('NY', 'New York', '2013-10-01'));

Answer 2

I think this should do the trick for you:

select 
    * 
from 
    data t1
natural join 
    ( 
        select 
            city, 
            state, 
            max(date) as date
        from 
            data
        group by 
            city, 
            state
    ) t2;