Get latest exchange rate for all currencies

Question

I have a database with a lot a currencies and each row has a currency, datestamp and the exchange rate. What I would like to have is a query that gets me the latest exchange rate for all the currencies based on the datestamp. I would not like the date in the result.

Is this possible easily? I am using pervasive 10

Answer 1

I've never worked with pervasive but this will work with most DBs.

SELECT 
    c.currency
    c.exchange_rate 

FROM  
      currencies  c
       INNER JOIN 
        (SELECT 

            MAX(datestamp) datestamp , Currency
        FROM 
            currencies 
         GROUP BY 
            Currency) current_exchange
        ON c.datestamp  = current_exchange.datestamp  
       and
      c.Currency = current_exchange.Currency